Threshold-based and power-efficient scheduling request procedure

ABSTRACT

The invention relates to methods for improving a scheduling request transmission between a UE and a base station. The transmission of the scheduling request is postponed, by implementing a threshold that the data in the transmission buffer has to reach, before a transmission of the scheduling request is triggered. In one variant, the data in the transmission buffer needs to reach a specific amount, to trigger a scheduling request. The invention refers to further improvements: the PDDCH monitoring time window is delayed after sending a scheduling request; the dedicated scheduling request resources of the PUCCH are prioritized differently such that low-priority scheduling requests are transmitted less often.

FIELD OF THE INVENTION

The invention relates to methods for improvements to the schedulingrequest procedure performed between a user equipment and a radio basestation. The invention is also providing the user equipment forperforming the methods described herein.

TECHNICAL BACKGROUND

Long Term Evolution (LTE) Third-generation mobile systems (3G) based onWCDMA radio-access technology are being deployed on a broad scale allaround the world. A first step in enhancing or evolving this technologyentails introducing High-Speed Downlink Packet Access (HSDPA) and anenhanced uplink, also referred to as High Speed Uplink Packet Access(HSUPA), giving a radio access technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies, 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support for the next decade.The ability to provide high bit rates is a key measure for LTE.

The work item (WI) specification on Long-Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial RadioAccess Network (UTRAN) is finalized as Release 8 (LTE Rel. 8). The LTEsystem represents efficient packet-based radio access and radio accessnetworks that provide full IP-based functionalities with low latency andlow cost. In LTE, scalable multiple transmission bandwidths arespecified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order toachieve flexible system deployment using a given spectrum. In thedownlink, Orthogonal Frequency Division Multiplexing (OFDM) based radioaccess was adopted because of its inherent immunity to multipathinterference (MPI) due to a low symbol rate, the use of a cyclic prefix(CP) and its affinity to different transmission bandwidth arrangements.Single-carrier frequency division multiple access (SC-FDMA) based radioaccess was adopted in the uplink, since provisioning of wide areacoverage was prioritized over improvement in the peak data rateconsidering the restricted transmit power of the user equipment (UE).Many key packet radio access techniques are employed includingmultiple-input multiple-output (MIMO) channel transmission techniquesand a highly efficient control signaling structure is achieved in LTERel. 8/9.

LTE Architecture

The overall architecture is shown in FIG. 1 and a more detailedrepresentation of the E-UTRAN architecture is given in FIG. 2. TheE-UTRAN consists of an eNodeB, providing the E-UTRA user plane(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towardsthe user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY),Medium Access Control (MAC), Radio Link Control (RLC) and Packet DataControl Protocol (PDCP) layers that include the functionality ofuser-plane header-compression and encryption. It also offers RadioResource Control (RRC) functionality corresponding to the control plane.It performs many functions including radio resource management,admission control, scheduling, enforcement of negotiated uplink Qualityof Service (QoS), cell information broadcast, ciphering/deciphering ofuser and control plane data, and compression/decompression ofdownlink/uplink user plane packet headers. The eNodeBs areinterconnected with each other by means of the X2 interface.

The eNodeBs are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g., parameters of the IP bearerservice, network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at time of intra-LTEhandover involving Core Network (CN) node relocation. It is responsiblefor authenticating the user (by interacting with the HSS). TheNon-Access Stratum (NAS) signaling terminates at the MME and it is alsoresponsible for generation and allocation of temporary identities touser equipments. It checks the authorization of the user equipment tocamp on the service provider's Public Land Mobile Network (PLMN) andenforces user equipment roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN. TheMME also terminates the S6a interface towards the home HSS for roaminguser equipments.

Component Carrier Structure in LTE (Release 8)

The downlink component carrier of a 3GPP LTE (Release 8) is subdividedin the time-frequency domain in so-called subframes. In 3GPP LTE(Release 8) each subframe is divided into two downlink slots as shown inFIG. 3, wherein the first downlink slot comprises the control channelregion (PDCCH region) within the first OFDM symbols. Each subframeconsists of a give number of OFDM symbols in the time domain (12 or 14OFDM symbols in 3GPP LTE (Release 8)), wherein each OFDM symbol spansover the entire bandwidth of the component carrier. The OFDM symbolsthus each consists of a number of modulation symbols transmitted onrespective N_(RB) ^(DL)×N_(sc) ^(RB) A subcarriers as also shown in FIG.4.

Assuming a multi-carrier communication system, e.g., employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”.A physical resource block is defined as N_(symb) ^(DL) consecutive OFDMsymbols in the time domain and N_(sc) ^(RB) consecutive subcarriers inthe frequency domain as exemplified in FIG. 4. In 3GPP LTE (Release 8),a physical resource block thus consists of N_(RB) ^(DL)×N_(sc) ^(RB)resource elements, corresponding to one slot in the time domain and 180kHz in the frequency domain (for further details on the downlinkresource grid, see for example 3GPP TS 36.211, “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 8)”, section 6.2, available at http://www.3gpp.org andincorporated herein by reference).

The term “component carrier” refers to a combination of several resourceblocks. In future releases of LTE, the term “component carrier” is nolonger used; instead, the terminology is changed to “cell”, which refersto a combination of downlink and optionally uplink resources. Thelinking between the carrier frequency of the downlink resources and thecarrier frequency of the uplink resources is indicated in the systeminformation transmitted on the downlink resources.

Further Advancements for LTE (LTE-A)

The frequency spectrum for IMT-Advanced was decided at the WorldRadiocommunication Conference 2007 (WRC-07). Although the overallfrequency spectrum for IMT-Advanced was decided, the actual availablefrequency bandwidth is different according to each region or country.Following the decision on the available frequency spectrum outline,however, standardization of a radio interface started in the 3rdGeneration Partnership Project (3GPP). At the 3GPP TSG RAN #39 meeting,the Study Item description on “Further Advancements for E-UTRA(LTE-Advanced)” was approved. The study item covers technologycomponents to be considered for the evolution of E-UTRA, e.g., tofulfill the requirements on IMT-Advanced. Two major technologycomponents are described in the following.

Carrier Aggregation in LTE-A for Support of Wider Bandwidth

The bandwidth that the LTE-Advanced system is able to support is 100MHz, while an LTE system can only support 20 MHz. Nowadays, the lack ofradio spectrum has become a bottleneck of the development of wirelessnetworks, and as a result it is difficult to find a spectrum band whichis wide enough for the LTE-Advanced system. Consequently, it is urgentto find a way to gain a wider radio spectrum band, wherein a possibleanswer is the carrier aggregation functionality.

In carrier aggregation, two or more component carriers (componentcarriers) are aggregated in order to support wider transmissionbandwidths up to 100 MHz. Several cells in the LTE system are aggregatedinto one wider channel in the LTE-Advanced system which is wide enoughfor 100 MHz even though these cells in LTE are in different frequencybands.

All component carriers can be configured to be LTE Rel. 8/9 compatible,at least when the aggregated numbers of component carriers in the uplinkand the downlink are the same. Not all component carriers aggregated bya user equipment may necessarily be Rel. 8/9 compatible. Existingmechanism (e.g., barring) may be used to avoid Rel-8/9 user equipmentsto camp on a component carrier.

A user equipment may simultaneously receive or transmit one or multiplecomponent carriers (corresponding to multiple serving cells) dependingon its capabilities. A LTE-A Rel. 10 user equipment with receptionand/or transmission capabilities for carrier aggregation cansimultaneously receive and/or transmit on multiple serving cells,whereas an LTE Rel. 8/9 user equipment can receive and transmit on asingle serving cell only, provided that the structure of the componentcarrier follows the Rel. 8/9 specifications.

Carrier aggregation is supported for both contiguous and non-contiguouscomponent carriers with each component carrier limited to a maximum of110 Resource Blocks in the frequency domain using the 3GPP LTE (Release8/9) numerology.

It is possible to configure a 3GPP LTE-A (Release 10) compatible userequipment to aggregate a different number of component carriersoriginating from the same eNodeB (base station) and of possiblydifferent bandwidths in the uplink and the downlink. The number ofdownlink component carriers that can be configured depends on thedownlink aggregation capability of the UE. Conversely, the number ofuplink component carriers that can be configured depends on the uplinkaggregation capability of the UE. It may not be possible to configure amobile terminal with more uplink component carriers than downlinkcomponent carriers.

In a typical TDD deployment, the number of component carriers and thebandwidth of each component carrier in uplink and downlink is the same.Component carriers originating from the same eNodeB need not to providethe same coverage.

The spacing between center frequencies of contiguously aggregatedcomponent carriers shall be a multiple of 300 kHz. This is in order tobe compatible with the 100 kHz frequency raster of 3GPP LTE (Release8/9) and at the same time preserve orthogonality of the subcarriers with15 kHz spacing. Depending on the aggregation scenario, the n×300 kHzspacing can be facilitated by insertion of a low number of unusedsubcarriers between contiguous component carriers.

The nature of the aggregation of multiple carriers is only exposed up tothe MAC layer. For both uplink and downlink there is one HARQ entityrequired in MAC for each aggregated component carrier. There is (in theabsence of SU-MIMO for uplink) at most one transport block per componentcarrier. A transport block and its potential HARQ retransmissions needto be mapped on the same component carrier.

The Layer 2 structure with activated carrier aggregation is shown inFIG. 5 and FIG. 6 for the downlink and uplink respectively. Thetransport channels are described between MAC and Layer 1, the logicalchannels are described between MAC and RLC.

When carrier aggregation is configured, the mobile terminal only has oneRRC connection with the network. At RRC connectionestablishment/re-establishment, one cell provides the security input(one ECGI, one PCI and one ARFCN) and the non-access stratum mobilityinformation (e.g., TAI) similarly as in LTE Rel. 8/9. After RRCconnection establishment/re-establishment; the component carriercorresponding to that cell is referred to as the downlink Primary Cell(PCell). There is always one and only one downlink PCell (DL PCell) andone uplink PCell (UL PCell) configured per user equipment in connectedstate. In the downlink, the carrier corresponding to the PCell is theDownlink Primary Component Carrier (DL PCC), while in the uplink it isthe Uplink Primary Component Carrier (UL PCC).

Depending on UE capabilities, Secondary Cells (SCells) can be configuredto form together with the PCell a set of serving cells. In the downlink,the carrier corresponding to an SCell is a Downlink Secondary ComponentCarrier (DL SCC), while in the uplink it is an Uplink SecondaryComponent Carrier (UL SCC).

The characteristics of the downlink and uplink PCell are:

-   -   For each SCell the usage of uplink resources by the UE in        addition to the downlink ones is configurable (the number of DL        SCCs configured is therefore always larger or equal to the        number of UL SCCs, and no SCell can be configured for usage of        uplink resources only)    -   The downlink PCell cannot be de-activated, unlike SCells    -   Re-establishment is triggered when the downlink PCell        experiences Rayleigh fading (RLF), not when downlink SCells        experience RLF    -   Non-access stratum information is taken from the downlink PCell    -   PCell can only be changed with handover procedure (i.e., with        security key change and RACH procedure)    -   PCell is used for transmission of PUCCH    -   The uplink PCell is used for transmission of Layer 1 uplink        control information    -   From a UE viewpoint, each uplink resource only belongs to one        serving cell

The configuration and reconfiguration of component carriers can beperformed by RRC. Activation and deactivation is done via MAC controlelements. At intra-LTE handover, RRC can also add, remove, orreconfigure SCells for usage in the target cell. When adding a newSCell, dedicated RRC signaling is used for sending the systeminformation of the SCell, the information being necessary fortransmission/reception (similarly as in Rel-8/9 for handover). In otherwords, while in connected mode, UEs need not acquire broadcast systeminformation directly from the SCells.

When a user equipment is configured with carrier aggregation there isone pair of uplink and downlink component carriers that is alwaysactive. The downlink component carrier of that pair might be alsoreferred to as ‘DL anchor carrier’. Same applies also for the uplink.

When carrier aggregation is configured, a user equipment may bescheduled over multiple component carriers simultaneously but at mostone random access procedure shall be ongoing at any time. Cross-carrierscheduling allows the PDCCH of a component carrier to schedule resourceson another component carrier. For this purpose a component carrieridentification field is introduced in the respective DCI formats, calledCIF.

A linking between uplink and downlink component carriers allowsidentifying the uplink component carrier for which the grant applieswhen there is no-cross-carrier scheduling. The linkage of downlinkcomponent carriers to uplink component carrier does not necessarily needto be one to one. In other words, more than one downlink componentcarrier can link to the same uplink component carrier. At the same time,a downlink component carrier can only link to one uplink componentcarrier.

LTE RRC States

LTE is based on only two main states: “RRC_IDLE” and “RRC_CONNECTED”.

In RRC_IDLE the radio is not active, but an ID is assigned and trackedby the network. More specifically, a mobile terminal in RRC_IDLEperforms cell selection and reselection—in other words, it decides onwhich cell to camp. The cell (re)selection process takes into accountthe priority of each applicable frequency of each applicable RadioAccess Technology (RAT), the radio link quality and the cell status(i.e., whether a cell is barred or reserved). An RRC_IDLE mobileterminal monitors a paging channel to detect incoming calls, and alsoacquires system information. The system information mainly consists ofparameters by which the network (E-UTRAN) can control the cell(re)selection process. RRC specifies the control signaling applicablefor a mobile terminal in RRC_IDLE, namely paging and system information.The mobile terminal behavior in RRC_IDLE is specified in TR 25.912,e.g., Chapter 8.4.2 incorporate herein by reference.

In RRC_CONNECTED the mobile terminal has an active radio operation withcontexts in the eNodeB. The E-UTRAN allocates radio resources to themobile terminal to facilitate the transfer of (unicast) data via shareddata channels. To support this operation, the mobile terminal monitorsan associated control channel which is used to indicate the dynamicallocation of the shared transmission resources in time and frequency.The mobile terminal provides the network with reports of its bufferstatus and of the downlink channel quality, as well as neighboring cellmeasurement information to enable E-UTRAN to select the most appropriatecell for the mobile terminal. These measurement reports include cellsusing other frequencies or RATs. The UE also receives systeminformation, consisting mainly of information required to use thetransmission channels. To extend its battery lifetime, a UE inRRC_CONNECTED may be configured with a Discontinuous Reception (DRX)cycle. RRC is the protocol by which the E-UTRAN controls the UE behaviorin RRC_CONNECTED.

FIG. 7 shows a state diagram with an overview of the relevant functionsperformed by the mobile terminal in IDLE and CONNECTED state.

Logical and Transport Channels

The MAC layer provides a data transfer service for the RLC layer throughlogical channels. Logical channels are either Control Logical Channelswhich carry control data such as RRC signaling, or Traffic LogicalChannels which carry user plane data. Broadcast Control Channel (BCCH),Paging Control channel (PCCH), Common Control Channel (CCCH), MulticastControl Channel (MCCH) and Dedicated Control Channel (DCCH) are ControlLogical Channels. Dedicated Traffic channel (DTCH) and Multicast TrafficChannel (MTCH) are Traffic Logical Channels.

Data from the MAC layer is exchanged with the physical layer throughTransport Channels. Data is multiplexed into transport channelsdepending on how it is transmitted over the air. Transport channels areclassified as downlink or uplink as follows. Broadcast Channel (BCH),Downlink Shared Channel (DL-SCH), Paging Channel (PCH) and MulticastChannel (MCH) are downlink transport channels, whereas the Uplink SharedChannel (UL-SCH) and the Random Access Channel (RACH) are uplinktransport channels.

A multiplexing is then performed between logical channels and transportchannels in the downlink and uplink respectively.

Layer 1/Layer 2 (L1/L2) Control Signaling

In order to inform the scheduled users about their allocation status,transport format and other data-related information (e.g., HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a subframe,assuming that the user allocation can change from subframe to subframe.It should be noted that user allocation might also be performed on a TTI(Transmission Time Interval) basis, where the TTI length is a multipleof the sub-frames. The TTI length may be fixed in a service area for allusers, may be different for different users, or may even by dynamic foreach user. Generally, the L1/2 control signaling needs only betransmitted once per TTI.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). A PDCCH carries a message as a Downlink ControlInformation (DCI), which includes resource assignments and other controlinformation for a mobile terminal or groups of UEs. In general, severalPDCCHs can be transmitted in one subframe.

It should be noted that in 3GPP LTE, assignments for uplink datatransmissions, also referred to as uplink scheduling grants or uplinkresource assignments, are also transmitted on the PDCCH.

With respect to scheduling grants, the information sent on the L1/L2control signaling may be separated into the following two categories,Shared Control Information (SCI) carrying Cat 1 information and DownlinkControl Information (DCI) carrying Cat 2/3 information.

Shared Control Information (SCI) Carrying Cat 1 Information

The shared control information part of the L1/L2 control signalingcontains information related to the resource allocation (indication).The shared control information typically contains the followinginformation:

-   -   A user identity indicating the user(s) that is/are allocated the        resources.    -   RB allocation information for indicating the resources (Resource        Blocks (RBs)) on which a user(s) is/are allocated. The number of        allocated resource blocks can be dynamic.    -   The duration of assignment (optional), if an assignment over        multiple sub-frames (or TTIs) is possible.

Depending on the setup of other channels and the setup of the DownlinkControl Information (DCI)—see below—the shared control information mayadditionally contain information such as ACK/NACK for uplinktransmission, uplink scheduling information, information on the DCI(resource, MCS, etc.).

Downlink Control Information (DCI) Carrying Cat 2/3 Information

The downlink control information part of the L1/L2 control signalingcontains information related to the transmission format (Cat 2information) of the data transmitted to a scheduled user indicated bythe Cat 1 information. Moreover, in case of using (Hybrid) ARQ as aretransmission protocol, the Cat 2 information carries HARQ (Cat 3)information. The downlink control information needs only to be decodedby the user scheduled according to Cat 1. The downlink controlinformation typically contains information on:

-   -   Cat 2 information: Modulation scheme, transport-block (payload)        size or coding rate, MIMO (Multiple Input Multiple        Output)-related information, etc. Either the transport-block (or        payload size) or the code rate can be signaled. In any case        these parameters can be calculated from each other by using the        modulation scheme information and the resource information        (number of allocated resource blocks)    -   Cat 3 information: HARQ related information, e.g., hybrid ARQ        process number, redundancy version, retransmission sequence        number

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in its fields. Thedifferent DCI formats that are currently defined for LTE are as followsand described in detail in 3GPP TS 36.212, “Multiplexing and channelcoding”, section 5.3.3.1 (available at http://www.3gpp.org andincorporated herein by reference).

Format 0: DCI Format 0 is used for the transmission of resource grantsfor the PUSCH.

For further information regarding the DCI formats and the particularinformation that is transmitted in the DCI, please refer to thetechnical standard or to LTE—The UMTS Long Term Evolution—From Theory toPractice, Edited by Stefanie Sesia, Issam Toufik, Matthew Baker, Chapter9.3, incorporated herein by reference.

Downlink & Uplink Data Transmission

Regarding downlink data transmission, L1/L2 control signaling istransmitted on a separate physical channel (PDCCH), along with thedownlink packet data transmission. This L1/L2 control signalingtypically contains information on:

-   -   The physical resource(s) on which the data is transmitted (e.g.,        subcarriers or subcarrier blocks in case of OFDM, codes in case        of CDMA). This information allows the mobile terminal (receiver)        to identify the resources on which the data is transmitted.    -   When user equipment is configured to have a Carrier Indication        Field (CIF) in the L1/L2 control signaling, this information        identifies the component carrier for which the specific control        signaling information is intended. This enables assignments to        be sent on one component carrier which are intended for another        component carrier (“cross-carrier scheduling”). This other,        cross-scheduled component carrier could be for example a        PDCCH-less component carrier, i.e., the cross-scheduled        component carrier does not carry any L1/L2 control signaling.    -   The Transport Format, which is used for the transmission. This        can be the transport block size of the data (payload size,        information bits size), the MCS (Modulation and Coding Scheme)        level, the Spectral Efficiency, the code rate, etc. This        information (usually together with the resource allocation        (e.g., the number of resource blocks assigned to the user        equipment)) allows the user equipment (receiver) to identify the        information bit size, the modulation scheme and the code rate in        order to start the demodulation, the de-rate-matching and the        decoding process. The modulation scheme may be signaled        explicitly.    -   Hybrid ARQ (HARQ) information:        -   HARQ process number: Allows the user equipment to identify            the hybrid ARQ process on which the data is mapped.        -   Sequence number or new data indicator (NDI): Allows the user            equipment to identify if the transmission is a new packet or            a retransmitted packet. If soft combining is implemented in            the HARQ protocol, the sequence number or new data indicator            together with the HARQ process number enables soft-combining            of the transmissions for a PDU prior to decoding.        -   Redundancy and/or constellation version: Tells the user            equipment, which hybrid ARQ redundancy version is used            (required for de-rate-matching) and/or which modulation            constellation version is used (required for demodulation).    -   UE Identity (UE ID): Tells for which user equipment the L1/L2        control signaling is intended for. In typical implementations        this information is used to mask the CRC of the L1/L2 control        signaling in order to prevent other user equipments to read this        information.

To enable an uplink packet data transmission, L1/L2 control signaling istransmitted on the downlink (PDCCH) to tell the user equipment about thetransmission details. This L1/L2 control signaling typically containsinformation on: The physical resource(s) on which the user equipmentshould transmit the data (e.g., subcarriers or subcarrier blocks in caseof OFDM, codes in case of CDMA).

-   -   When user equipment is configured to have a Carrier Indication        Field (CIF) in the L1/L2 control signaling, this information        identifies the component carrier for which the specific control        signaling information is intended. This enables assignments to        be sent on one component carrier which are intended for another        component carrier. This other, cross-scheduled component carrier        may be for example a PDCCH-less component carrier, i.e., the        cross-scheduled component carrier does not carry any L1/L2        control signaling.    -   L1/L2 control signaling for uplink grants is sent on the DL        component carrier that is linked with the uplink component        carrier or on one of the several DL component carriers, if        several DL component carriers link to the same UL component        carrier.    -   The Transport Format, the user equipment should use for the        transmission. This can be the transport block size of the data        (payload size, information bits size), the MCS (Modulation and        Coding Scheme) level, the Spectral Efficiency, the code rate,        etc. This information (usually together with the resource        allocation (e.g., the number of resource blocks assigned to the        user equipment)) allows the user equipment (transmitter) to pick        the information bit size, the modulation scheme and the code        rate in order to start the modulation, the rate-matching and the        encoding process. In some cases the modulation scheme maybe        signaled explicitly.    -   Hybrid ARQ information:        -   HARQ Process number: Tells the user equipment from which            hybrid ARQ process it should pick the data.        -   Sequence number or new data indicator: Tells the user            equipment to transmit a new packet or to retransmit a            packet. If soft combining is implemented in the HARQ            protocol, the sequence number or new data indicator together            with the HARQ process number enables soft-combining of the            transmissions for a protocol data unit (PDU) prior to            decoding.        -   Redundancy and/or constellation version: Tells the user            equipment, which hybrid ARQ redundancy version to use            (required for rate-matching) and/or which modulation            constellation version to use (required for modulation).    -   UE Identity (UE ID): Tells which user equipment should transmit        data. In typical implementations this information is used to        mask the CRC of the L1/L2 control signaling in order to prevent        other user equipments to read this information.

There are several different possibilities how to exactly transmit theinformation pieces mentioned above in uplink and downlink datatransmission. Moreover, in uplink and downlink, the L1/L2 controlinformation may also contain additional information or may omit some ofthe information. For example:

-   -   HARQ process number may not be needed, i.e., is not signaled, in        case of a synchronous HARQ protocol.    -   A redundancy and/or constellation version may not be needed, and        thus not signaled, if Chase Combining is used (always the same        redundancy and/or constellation version) or if the sequence of        redundancy and/or constellation versions is pre-defined.    -   Power control information may be additionally included in the        control signaling.    -   MIMO related control information, such as, e.g., pre-coding, may        be additionally included in the control signaling.    -   In case of multi-codeword MIMO transmission transport format        and/or HARQ information for multiple code words may be included.

For uplink resource assignments (on the Physical Uplink Shared Channel(PUSCH)) signaled on PDCCH in LTE, the L1/L2 control information doesnot contain a HARQ process number, since a synchronous HARQ protocol isemployed for LTE uplink. The HARQ process to be used for an uplinktransmission is given by the timing. Furthermore, it should be notedthat the redundancy version (RV) information is jointly encoded with thetransport format information, i.e., the RV info is embedded in thetransport format (TF) field. The Transport Format (TF) respectivelymodulation and coding scheme (MCS) field has for example a size of 5bits, which corresponds to 32 entries. 3 TF/MCS table entries arereserved for indicating redundancy versions (RVs) 1, 2 or 3. Theremaining MCS table entries are used to signal the MCS level (TBS)implicitly indicating RV0. The size of the CRC field of the PDCCH is 16bits.

For downlink assignments (PDSCH) signaled on PDCCH in LTE the RedundancyVersion (RV) is signaled separately in a two-bit field. Furthermore themodulation order information is jointly encoded with the transportformat information. Similar to the uplink case there is 5 bit MCS fieldsignaled on PDCCH. 3 of the entries are reserved to signal an explicitmodulation order, providing no Transport format (Transport block) info.For the remaining 29 entries modulation order and Transport block sizeinfo are signaled.

DRX (Discontinuous Reception)

DRX functionality can be configured for RRC_IDLE, in which case the UEuses either the specific or default DRX value (defaultPagingCycle); thedefault is broadcasted in the System Information, and can have values of32, 64, 128 and 256 radio frames. If both specific and default valuesare available, the shorter value of the two is chosen by the UE. The UEneeds to wake up for one paging occasion per DRX cycle, the pagingoccasion being one subframe.

DRX functionality can be also configured for an “RRC_CONNECTED” UE, sothat it does not always need to monitor the downlink channels. In orderto provide reasonable battery consumption of user equipment, 3GPP LTE(Release 8/9) as well as 3GPP LTE-A (Release 10) provides a concept ofdiscontinuous reception (DRX). Technical Standard TS 36.321 Chapter 5.7explains the DRX and is incorporated by reference herein.

The following parameters are available to define the DRX UE behavior;i.e., the On-Duration periods at which the mobile node is active, andthe periods where the mobile node is in a DRX mode.

-   -   On duration: duration in downlink sub-frames that the user        equipment, after waking up from DRX, receives and monitors the        PDCCH. If the user equipment successfully decodes a PDCCH, the        user equipment stays awake and starts the inactivity timer;        [1-200 subframes; 16 steps: 1-6, 10-60, 80, 100, 200]    -   DRX inactivity timer: duration in downlink sub-frames that the        user equipment waits to successfully decode a PDCCH, from the        last successful decoding of a PDCCH; when the UE fails to decode        a PDCCH during this period, it re-enters DRX. The user equipment        shall restart the inactivity timer following a single successful        decoding of a PDCCH for a first transmission only (i.e., not for        retransmissions). [1-2560 subframes; 22 steps, 10 spares: 1-6,        8, 10-60, 80, 100-300, 500, 750, 1280, 1920, 2560]    -   DRX Retransmission timer: specifies the number of consecutive        PDCCH subframes where a downlink retransmission is expected by        the UE after the first available retransmission time. [1-33        subframes, 8 steps: 1, 2, 4, 6, 8, 16, 24, 33]    -   DRX short cycle: specifies the periodic repetition of the on        duration followed by a possible period of inactivity for the        short DRX cycle. This parameter is optional. [2-640 subframes;        16 steps: 2, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256,        320, 512, 640]    -   DRX short cycle timer: specifies the number of consecutive        subframes the UE follows the short DRX cycle after the DRX        Inactivity Timer has expired. This parameter is optional. [1-16        subframes]    -   Long DRX Cycle Start offset: specifies the periodic repetition        of the on duration followed by a possible period of inactivity        for the DRX long cycle as well as an offset in subframes when        on-duration starts (determined by formula defined in TS 36.321        section 5.7); [cycle length 10-2560 subframes; 16 steps: 10, 20,        30, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280,        2048, 2560; offset is an integer between [0−subframe length of        chosen cycle]]

The total duration that the UE is awake is called “Active time”. TheActive Time includes the on-duration of the DRX cycle, the time UE isperforming continuous reception while the inactivity timer has notexpired and the time UE is performing continuous reception while waitingfor a downlink retransmission after one HRQ RTT. Similarly, for theuplink the UE is awake at the subframes where uplink retransmissiongrants can be received, i.e., every 8 ms after initial uplinktransmission until maximum number of retransmissions is reached. Basedon the above, the minimum active time is of fixed length equal toon-duration, and the maximum is variable depending on, e.g., the PDCCHactivity.

The operation of DRX gives the mobile terminal the opportunity todeactivate the radio circuits repeatedly (according to the currentlyactive DRX cycle) in order to save power. Whether the UE indeed remainsin DRX (i.e., is not active) during the DRX period may be decided by theUE; for example, the UE usually performs inter-frequency measurementswhich cannot be conducted during the On-Duration, and thus need to beperformed some other time, during the DRX opportunity of time.

The parameterization of the DRX cycle involves a trade-off betweenbattery saving and latency. For example, in case of a web browsingservice, it is usually a waste of resources for a UE to continuouslyreceive downlink channels while the user is reading a downloaded webpage. On the one hand, a long DRX period is beneficial for lengtheningthe UE's battery life. On the other hand, a short DRX period is betterfor faster response when data transfer is resumed—for example when auser requests another web page.

To meet these conflicting requirements, two DRX cycles—a short cycle anda long cycle—can be configured for each UE; the short DRX cycle isoptional, i.e., only the long DRX cycle is used. The transition betweenthe short DRX cycle, the long DRX cycle and continuous reception iscontrolled either by a timer or by explicit commands from the eNodeB. Insome sense, the short DRX cycle can be considered as a confirmationperiod in case a late packet arrives, before the UE enters the long DRXcycle. If data arrives at the eNodeB while the UE is in the short DRXcycle, the data is scheduled for transmission at the next on-durationtime, and the UE then resumes continuous reception. On the other hand,if no data arrives at the eNodeB during the short DRX cycle, the UEenters the long DRX cycle, assuming that the packet activity is finishedfor the time being.

During the Active Time the UE monitors PDCCH, reports SRS (SoundingReference Signal) as configured and reports CQI (Channel QualityInformation)/PMI (Precoding Matrix Indicator)/RI (Rank Indicator)/PTI(Precoder Type Indication) on PUCCH. When UE is not in Active time,type-0-triggered SRS and CQI/PMI/RI/PTI on PUCCH may not be reported. IfCQI masking is set up for the UE, the reporting of CQI/PMI/RI/PTI onPUCCH is limited to On Duration. Available DRX values are controlled bythe network and start from non-DRX up to x seconds. Value x may be aslong as the paging DRX used in RRC_IDLE. Measurement requirements andreporting criteria can differ according to the length of the DRXinterval, i.e., long DRX intervals may have more relaxed requirements(for more details see further below). When DRX is configured, periodicCQI reports can only be sent by the UE during “active-time”. RRC canfurther restrict periodic CQI reports so that they are only sent duringthe on-duration.

FIG. 8 discloses an example of DRX. The UE checks for schedulingmessages (indicated by its C-RNTI, cell radio network temporaryidentity, on the PDCCH) during the “on duration” period, which is thesame for the long DRX cycle and the short DRX cycle. When a schedulingmessage is received during an “on duration”, the UE starts an“inactivity timer” and monitors the PDCCH in every subframe while theInactivity Timer is running. During this period, the UE can be regardedas being in a continuous reception mode. Whenever a scheduling messageis received while the Inactivity Timer is running, the UE restarts theInactivity Timer, and when it expires the UE moves into a short DRXcycle and starts a “short DRX cycle timer”. The short DRX cycle may alsobe initiated by means of a MAC Control Element. When the short DRX cycletimer expires, the UE moves into a long DRX cycle.

In addition to this DRX behavior, a ‘HARQ Round Trip Time (RTT) timer’is defined with the aim of allowing the UE to sleep during the HARQ RTT.When decoding of a downlink transport block for one HARQ process fails,the UE can assume that the next retransmission of the transport blockwill occur after at least ‘HARQ RTT’ subframes. While the HARQ RTT timeris running, the UE does not need to monitor the PDCCH. At the expiry ofthe HARQ RTT timer, the UE resumes reception of the PDCCH as normal.

There is only one DRX cycle per user equipment. All aggregated componentcarriers follow this DRX pattern.

Machine to Machine

The current mobile networks are optimally designed for Human-to-Humancommunications, but are less optimal for M2M (Machine-2-Machine)applications, which according to 3GPP is also termed MTC(Machine-Type-Communication).

M2M Communication can be seen as a form of data communication betweenentities that do not necessarily need human interaction. It is differentto current communication models as it involves new or different marketscenarios, lower costs and effort, a potentially very large number ofcommunicating terminals and little traffic per terminal to a largeextent.

Some MTC applications are for example:

-   -   Security (e.g., Alarm Systems, Backup for landline, Access        Control, Car/Driver security)    -   Tracking & Tracing (e.g., Fleet Management, Order Management,        Pay as you drive, Road Tolling, Traffic information)    -   Payment (Point of Sales, Vending machines, Loyalty Concepts,        Gaming machines)    -   Health (Monitoring vital signs, Remote diagnostics, Web Access        Telemedicine point)    -   Remote Maintenance/Control (Sensors, Lighting, Pumps, Valves,        Elevator control)    -   Metering (e.g., Power, Gas, Water, Heating, Grid Control)

A study item on M2M communications (3GPP TR 22.868) was completed in2007. For Rel-10 and beyond, 3GPP intends to take the results on networkimprovements from the study item forward into a specification phase andaddress the architectural impacts and security aspects to support MTCscenarios and applications. As such, 3GPP has defined a work item onNetwork Improvements for Machine-Type Communication (NIMTC) withdifferent goals and objectives such as to reduce the impact and effortof handling large machine-type communication groups, optimize networkoperations to minimize impact on device battery power usage, stimulatenew machine-type communication applications by enabling operators tooffer services tailored to machine-type communication requirements orprovide network operators with lower operational costs when offeringmachine-type communication services.

The MTC has some specifics that are different from the usualhuman-to-human communication. 3GPP tries to identify these specifics inorder to optimize the network operations. These specifics are called“MTC features” and are explained in the technical standard TS 22.368available from http://www.3gpp.org and incorporated herein by reference.For example, one of the mentioned MTC feature can be “small datatransmissions”, meaning that the MTC device sends or receives smallamounts of data. Small amount of data means that the data is smaller orcomparable with the size of the exchanged signaling needed to establishthe data connection.

Extra low-power consumption is also considered as a critical requirementfor some types of MTC devices. For some devices, such as those used forgas metering and animal, cargo, prisoner, elderly and children tracking,low power consumption is critical because it is not easy to recharge orreplace the battery. This creates the need for enhancements that wouldminimize the power consumption of MTC devices. Enhancements foroptimizing battery consumption can be foreseen on the architecture levelas well as on a lower layer protocol level such as PHY/MAC.

Moreover, LTE RAN enhancements for diverse data applications are understudy in 3GPP. The machine type communication traffic profiles includesporadic data access for exchange of relatively small data amounts. Sucha type of communication is particularly relevant for applications whichrequire always-on connectivity, such as smart phones, sporadic accessfor the purpose of checking e-mails or social network updates. The aimof the working items is to identify and specify mechanisms at the radioaccess network level that enable enhancing the ability of the LTE tohandle diverse traffic profiles. In particular, the aim is to reduce thepower usage of the terminals in order to extend the battery life. Themachine type communication traffic is in general delay insensitive, inwhich terminals and/or eNodeB can wait for some time until the data isdelivered.

Uplink Access Scheme for LTE

For Uplink transmission, power-efficient user-terminal transmission isnecessary to maximize coverage. Single-carrier transmission combinedwith FDMA with dynamic bandwidth allocation has been chosen as theevolved UTRA uplink transmission scheme. The main reason for thepreference for single-carrier transmission is the lower peak-to-averagepower ratio (PAPR), compared to multi-carrier signals (OFDMA), and thecorresponding improved power-amplifier efficiency and assumed improvedcoverage (higher data rates for a given terminal peak power). Duringeach time interval, Node B assigns users a unique time/frequencyresource for transmitting user data thereby ensuring intra-cellorthogonality. An orthogonal access in the uplink promises increasedspectral efficiency by eliminating intra-cell interference. Interferencedue to multipath propagation is handled at the base station (Node B),aided by insertion of a cyclic prefix in the transmitted signal.

The basic physical resource used for data transmission consists of afrequency resource of size BW_(grant) during one time interval, e.g., asub-frame of 0.5 ms, onto which coded information bits are mapped. Itshould be noted that a sub-frame, also referred to as transmission timeinterval (TTI), is the smallest time interval for user datatransmission. It is however possible to assign a frequency resourceBW_(grant) over a longer time period than one TTI to a user byconcatenation of sub-frames.

Uplink Scheduling Scheme for LTE

The uplink scheme allows for both scheduled access, i.e., controlled byeNB, and contention-based access.

In case of scheduled access, the UE is allocated a certain frequencyresource for a certain time (i.e., a time/frequency resource) for uplinkdata transmission. However, some time/frequency resources can beallocated for contention-based access; within these time/frequencyresources, UEs can transmit without first being scheduled. One scenariowhere UE is making a contention-based access is for example the randomaccess, i.e., when UE is performing initial access to a cell or forrequesting uplink resources.

For the scheduled access the Node B scheduler assigns a user a uniquefrequency/time resource for uplink data transmission. More specificallythe scheduler determines

-   -   which UE(s) that is (are) allowed to transmit,    -   which physical channel resources (frequency),    -   Transport format (Modulation Coding Scheme (MCS)) to be used by        the mobile terminal for transmission

The allocation information is signaled to the UE via a scheduling grant,sent on the L1/L2 control channel. For simplicity reasons this channelmay be called uplink grant channel in the following. A scheduling grantmessage contains at least information which part of the frequency bandthe UE is allowed to use, the validity period of the grant and thetransport format the UE has to use for the upcoming uplink transmission.The shortest validity period is one subframe. Additional information mayalso be included in the grant message, depending on the selected scheme.Only “per UE” grants are used to grant the right to transmit on theUL-SCH (i.e., there are no “per UE per RB” grants). Therefore, the UEneeds to distribute the allocated resources among the radio bearersaccording to some rules. Unlike in HSUPA there is no UE-based transportformat selection. The eNB decides the transport format based on someinformation, e.g., reported scheduling information and QoS info, and UEhas to follow the selected transport format. In HSUPA the Node B assignsthe maximum uplink resource, and the UE selects accordingly the actualtransport format for the data transmissions.

Since the scheduling of radio resources is the most important functionin a shared channel access network for determining Quality of service,there are a number of requirements that should be fulfilled by the ULscheduling scheme for LTE in order to allow for an efficient QoSmanagement.

-   -   Starvation of low priority services should be avoided    -   Clear QoS differentiation for radio bearers/services should be        supported by the scheduling scheme    -   The UL reporting should allow fine granular buffer status        reports (e.g., per radio bearer or per radio bearer group) in        order to allow the eNB scheduler to identify for which Radio        Bearer/service data is to be sent    -   It should be possible to make clear QoS differentiation between        services of different users    -   It should be possible to provide a minimum bit rate per radio        bearer

As can be seen from the above list, one essential aspect of the LTEscheduling scheme is to provide mechanisms with which the operator cancontrol the partitioning of its aggregated cell capacity between theradio bearers of the different QoS classes. The QoS class of a radiobearer is identified by the QoS profile of the corresponding SAE bearersignaled from AGW to eNB as described before. An operator can thenallocate a certain amount of its aggregated cell capacity to theaggregated traffic associated with radio bearers of a certain QoS class.The main goal of employing this class-based approach is to be able todifferentiate the treatment of packets depending on the QoS class theybelong to.

Buffer Status/Scheduling Request Reporting

The usual mode of scheduling is dynamic scheduling, by means of downlinkassignment messages for the allocation of downlink transmissionresources and uplink grant messages for the allocation of uplinktransmission resources; these are usually valid for specific singlesubframes. They are transmitted on the PDCCH using C-RNTI of the UE asalready mentioned before. Dynamic scheduling is efficient for servicestypes, in which the traffic is bursty and dynamic in rate, such as TCP.

In addition to the dynamic scheduling, a persistent scheduling isdefined, which enables radio resources to be semi-statically configuredand allocated to a UE for a longer time period than one subframe, thusavoiding the need for specific downlink assignment messages or uplinkgrant messages over the PDCCH for each subframe. Persistent schedulingis useful for services such as VoIP for which the data packets aresmall, periodic and semi-static in size. Thus, the overhead of the PDCCHis significantly reduced compared to the case of dynamic scheduling.

Buffer status reports (BSR) from the UE to the eNodeB are used to assistthe eNodeB in allocating uplink resources, i.e., uplink scheduling. Forthe downlink case, the eNB scheduler is obviously aware of the amount ofdata to be delivered to each UE; however, for the uplink direction,since scheduling decisions are done at the eNB and the buffer for thedata is in the UE, BSRs have to be sent from the UE to the eNB in orderto indicate the amount of data that needs to be transmitted over theUL-SCH.

Buffer Status Report MAC control elements for LTE consist of either: along BSR (with four buffer size fields corresponding to LCG IDs #0-3) ora short BSR (with one LCG ID field and one corresponding buffer sizefield). The buffer size field indicates the total amount of dataavailable across all logical channels of a logical channel group, and isindicated in number of bytes encoded as an index of different buffersize levels (see also 3GPP TS 36.321 v 10.5.0 Chapter 6.1.3.1,incorporated herewith by reference).

Which one of either the short or the long BSR is transmitted by the UEdepends on the available transmission resources in a transport block, onhow many groups of logical channels have non-empty buffers and onwhether a specific event is triggered at the UE. The long BSR reportsthe amount of data for four logical channel groups, whereas the shortBSR indicates the amount of data buffered for only the highest logicalchannel group.

The reason for introducing the logical channel group concept is thateven though the UE may have more than four logical channels configured,reporting the buffer status for each individual logical channel wouldcause too much signaling overhead. Therefore, the eNB assigns eachlogical channel to a logical channel group; preferably, logical channelswith same/similar QoS requirements should be allocated within the samelogical channel group.

In order to be robust against transmission failures, there is a BSRretransmission mechanism defined for LTE; the retransmission BSR timeris started or restarted whenever an uplink grant is restarted; if nouplink grant is received before the retransmission BSR timer expires,another BSR is triggered by the UE.

A BSR is triggered for events, such as:

-   -   Whenever data arrives for a logical channel, which has a higher        priority than the logical channels whose buffer are non-empty        (i.e., whose buffer previously contained data);    -   Whenever data becomes available for any logical channel, when        there was previously no data available for transmission (i.e.,        all buffers previously empty)    -   Whenever the retransmission BSR time expires    -   Whenever periodic BSR reporting is due, i.e., periodicBSR timer        expires    -   Whenever there is a spare space in a transport block which can        accommodate a BSR

More detailed information with regard to BSR and in particular thetriggering of same is explained in 3GPP TS 36.321 V10.5 in Chapter 5.4.5incorporated herewith by reference.

If the UE has no uplink resources allocated for including a BSR in thetransport block when a BSR is triggered, the UE sends a schedulingrequest (SR) to the eNodeB so as to be allocated with uplink resourcesto transmit the BSR. Either a single-bit scheduling request is sent overthe PUCCH (dedicated scheduling request, D-SR), or the random accessprocedure is performed to request an allocation of an uplink radioresource for sending a BSR.

However, for sake of completion it should be noted that the UE will nottrigger the transmission of the Scheduling Request for the case that aperiodic BSR is to be transmitted.

Furthermore, an enhancement to the SR transmission has been introducedfor the specific scheduling mode where resources are persistentlyallocated with a defined periodicity in order to save L1/L2 controlsignaling overhead for transmission grants, which is referred to assemi-persistent scheduling (SPS). One example for a service, which hasbeen mainly considered for semi-persistent scheduling, is VoIP. Every 20ms a VoIP packet is generated at the Codec during a talking spurt.Therefore, the eNodeB can allocate uplink or respectively downlinkresources persistently every 20 ms, which could then be used for thetransmission of VoIP packets. In general, SPS is beneficial for serviceswith predictable traffic behavior, i.e., constant bit rate, packetarrival time is periodic. For the case where SPS is configured for theuplink direction, the eNodeB can turn off SR triggering/transmission forcertain configured logical channels, i.e., BSR triggering due to dataarrival on those specific configured logical channels will not triggeran SR. The motivation for such kind of enhancements is that sending aScheduling Request for those logical channels which will use thesemi-persistently allocated resources (logical channels which carry VoIPpackets) is of no value for eNB scheduling and hence should be avoided.

Disadvantages of the Prior Art

A current work item in LTE relates to RAN Enhancements for Diverse DataApplications. The idea is to enhance current mobile networks to bettersupport smartphones, laptops, netbooks, tablets and embedded modemsrunning a wide variety of data applications, often in parallel. The maingoal is to identify and specify mechanisms at the radio access networklevel that enhance the ability of LTE to handle diverse trafficprofiles. The diversity and unpredictable nature of application trafficprofiles leads to challenges in optimizing the network and inguaranteeing efficient operation under all use cases. RRC state controlmechanisms and DRX configurations may be optimized with particularapplications in mind, but these may not remain optimal as differentapplications are installed/started/stopped on the device and as theconsequent traffic profile of the device changes over time. A furtheraim is to reduce the power usage of the terminals in order to extend thebattery life. Also, for certain MTC devices low power consumption mightbe a very critical requirement.

The currently standardized reporting of the buffer status report and thescheduling request is not power efficient, as will be explained in thefollowing with reference to FIG. 9.

FIG. 9 illustrates in an exemplary way the UE behavior relating toBSR/SR when data arrives in the transmission buffer of the UE (UE Txbuffer). For explanatory purposes the following somewhat simplifiedscenario is assumed. Only one transmission buffer and one logicalchannel of a UE is considered. The transmission buffer is assumed to beempty at the beginning, i.e., no data is stored in the transmissionbuffer. Furthermore, the UE shall not have sufficient uplink resourcesto transmit a buffer status report to the eNodeB. However, the UE shallhave semi-statically (by means of RRC signaling) allocated resourcesavailable in the PUCCH for transmitting a scheduling request (alsoreferred to as dedicated scheduling request, D-SR), when necessary.

Of course, the problem applies correspondingly to transmission buffersof other logical channels, as well as to a logical channel group wherethe transmission buffers of the logical channels grouped into thelogical channel group are considered together. Also, the transmissionbuffer(s) need not be empty; in said case however, the new data (i.e.,the data that currently arrives) entering the transmission buffer of theUE shall have a higher priority than the data already previously storedin the transmission buffer. Instead of using the allocated resources ofthe PUCCH for transmitting the SR, the UE might have to perform a RACHprocedure to transmit the scheduling request in case no such D-SR uplinkresources are available.

When new data arrives in the transmission buffer of the UE at time t1,the UE has to first request uplink resources for transmission of thedata since no appropriate uplink resources are momentarily available insaid respect. Thus, according to the standard trigger condition asexplained above, a BSR is triggered in the UE, and in view of the lackof uplink resources for transmitting even the BSR, a scheduling requestis triggered in the UE for transmission.

The UE uses the allocated PUCCH resources (or RACH procedure not shownin FIG. 9) to transmit the scheduling request to the eNodeB so as torequest the eNodeB to allocate uplink resources to the UE. Accordingly,the eNodeB allocates some UL-SCH resources to the UE. Depending, e.g.,on the current resource usage in the uplink, the eNodeB may allocateless or more uplink resources to the UE in response to the SR, and willtransmit a corresponding uplink grant via the PDCCH.

Upon receiving the uplink grant message, the UE may or may not transmitdata in addition to the BSR, depending on the amount of allocated PUSCHresources. When generating the BSR, this is considered by the UE, suchthat the BSR indicates the amount of data in the transmission bufferafter transmitting the BSR and possibly data of the transmission buffer.

Thus, the UE will transmit over the PUSCH only the BSR or may alsoinclude some data of the UE transmission buffer. In FIG. 9 in the firstsignaling exchange, it is assumed that the UE can transmit all data ofthe transmission buffer to the eNodeB using the uplink resourcesassigned by the eNodeB in response to the SR. Correspondingly, the BSRinforms the eNodeB about basically an empty transmission buffer, suchthat no further uplink grant is necessary to be allocated.

However, usually more than one uplink transmission will be necessary inorder to empty the transmission buffer, as is also illustrated in FIG. 9in connection with new data arriving at time t2. In this case, theamount of data is larger than the data becoming available in thetransmission buffer at time t1. However, the above procedure basicallyrepeats itself as illustrated, with the exception that the PUSCHtransmission, including the BSR and the data, does not suffice to emptythe transmission buffer. Correspondingly, the BSR generated by the UE atthe time of transmission informs the eNodeB about the remaining data inthe transmission buffer. The eNodeB thus will allocate to the UE furtheruplink resources in correspondence with the remaining data in thetransmission buffer. An uplink grant message is transmitted by theeNodeB to the UE, which in turn can then use the assigned uplinkresources to transmit the remaining data and thus empty its transmissionbuffer.

Each time new data arrives in the buffer, one of the above procedurewill be repeated. Hence, e.g., for low-volume backgroundservices/Instant Messaging services where only a small amount of dataneeds to be transmitted in certain frequent intervals (though intervalsdoes not need to be periodically) the currently defined BSR/SR procedureas of FIG. 9 is not efficient from the transmission power point of view.The frequent transmissions of SR/BSR consumes a lot of transmit power atthe UE. Further, also the PDCCH overhead (i.e., uplink grants) cannot beneglected since the eNodeB needs to issue many PDCCHs in order toschedule frequent PUSCH transmissions.

SUMMARY OF THE INVENTION

The present invention strives to avoid the various disadvantagesmentioned above.

One object of the invention is to propose a mechanism for an improvedscheduling request operation at the mobile terminal.

The object is solved by the subject matter of the independent claims.Advantageous embodiments are subject to the dependent claims.

According to a first aspect, the invention suggests an improvement tothe scheduling request transmission and thus to how resources arerequested by the user equipment. One of the main points regarding thisfirst aspect is that the transmission of a scheduling request shall bepostponed for particular situations in order to improve the powerefficiency of the UE. How this delaying of the transmission of thescheduling request may be achieved will be explained in the following.

Basically the same scenario is assumed as done with regard to FIG. 9 andthe explanation of the problem. In particular, a user equipment in acommunication system is supposed to have at least one transmissionbuffer for temporarily storing data to be transmitted in the uplink to aradio base station. Also, the user equipment shall have no uplinkresources available to transmit the buffer status report or any otherkind of user data; nevertheless and though not necessary for the purposeof this invention, the user equipment may have allocated periodicresources in the uplink control channel, sufficient to transmit ascheduling request (usually one bit) when necessary, but not enough totransmit more data.

In order to delay the transmission of the scheduling request, thetriggering of same is made threshold-dependent. More specifically, twotrigger conditions are defined in the UE, which when both are fulfilledeventually leads to the transmission of the scheduling request; bothtrigger conditions relate to triggering a transmission of a bufferstatus report to the radio base station, which in the absence ofappropriate uplink resources directly causes the transmission of ascheduling request to request allocation of appropriate uplink resourcesfor the transmission of the buffer status report (and possibly used fortransmission of data too).

The first trigger condition advantageously relates to new data becomingavailable in the transmission buffer; in other words, in order for thefirst trigger condition to be fulfilled, new data shall have to betransmitted by the user equipment and thus enters the correspondingtransmission buffer of the user equipment. This is independent ofwhether the transmission buffer is empty or not.

The second trigger condition relates to the data in the transmissionbuffer of the user equipment to exceed some threshold. One possibilityis that the second trigger condition comes true when the amount of datain the transmission buffer is higher than a predetermined amount ofdata, i.e., surpasses a data quantity threshold. Another possibility isto predetermine an amount of time, and starting when new data arrives inan empty transmission buffer, the second trigger condition triggers whenthe predetermined amount of time expires. Preferably, it should be notedthat said timer is not restarted (or reset) every time new data arrivesin the transmission buffer, but only once when “first” new data arrivesin an empty transmission buffer. Considering periodic uplink serviceswhere data is periodically generated and entered into the transmissionbuffer to be transmitted to the radio base station, the use of such atimer has quite a similar effect as when using a data quantity thresholdwhich has to be exceeded by the amount of data in the transmissionbuffer for the second trigger condition to be fulfilled.

These two possibilities for the second trigger condition are however notthe same, as apparent when considering that the expiry of a timer mighthappen even without new data arriving. Thus, when the second triggercondition requires a data quantity threshold to be exceeded, this canbasically only happen when new data arrives in the transmission bufferthus executing the first trigger condition, and the first and the secondtrigger condition are fulfilled at basically the same time. Of course,also in this case, instead of checking the first trigger condition everytime new data arrives, the fact that the first trigger condition isfulfilled can be stored the first time it is determined and as long asthe second trigger condition is checked, such that when the secondtrigger condition is determined to be fulfilled the scheduling requestis triggered without checking again the first trigger condition.

In contrast thereto, in case a timer is used as the second triggercondition, the first trigger condition does not have to be fulfilled forthe second trigger condition to be fulfilled; thus, with this timerpossibility, the user equipment may store that the first triggercondition is fulfilled as long as this timer runs, in which case whenthe timer expires, both trigger conditions are considered to come trueby the user equipment.

According to one variant of this first aspect, the buffer status report,and thus the scheduling request, is only triggered in case both triggerconditions are fulfilled; in other words, only when new data arrives inthe transmission buffer and data in the transmission buffer is more thana predetermined amount of data (or a timer, started when new dataarrives in the empty transmission buffer, expires).

Correspondingly, when both trigger conditions are fulfilled, the userequipment triggers the transmission of a buffer status report, and as adirect consequence (assuming no appropriate uplink resources areavailable), it can be said to trigger the transmission of a schedulingrequest. The scheduling request is transmitted to the radio basestation, either using an uplink control channel with allocatedpersistent resources (PUCCH) or using a random access procedure (RACH).

In a variant of the first aspect, the above-mentioned first triggercondition can be defined in accordance with the 3GPP standard (sebackground section), i.e., new data arrives in the transmission bufferwhen the transmission buffer is empty, and when the transmission is notempty (i.e., data is already stored in the transmission buffer awaitinguplink transmission) the first trigger condition shall be onlyfulfilled, in case the new data has a higher priority than the dataalready stored in the transmission buffer. In said case however, theuser equipment may store the information of the first trigger conditionbeing fulfilled for the following reason. Assuming that the firsttrigger condition is defined as currently in the standard, when thetransmission buffer is not empty, and new data arrives, the firsttrigger condition would not be fulfilled, since the newly arrived datadoes not necessarily have a higher priority, but most likely the samepriority, as the data already stored in the transmission buffer. Whennew data arrives in an empty buffer, and the first trigger condition istrue, this information of the first trigger condition being fulfilled isstored while determining whether the second trigger condition isfulfilled. By keeping the first trigger condition true for as long asnecessary, when determining whether the second trigger condition isfulfilled it is possible to delay the triggering of the buffer statusreport/scheduling request compared to the standard way of triggering.

According to a second aspect which can be used in combination orindependent from the above first aspect, the time during which the userequipment monitors the downlink control channel for an uplink grantafter sending the scheduling request via the dedicated resources of theuplink control channel (PUCCH) is shortened. As explained with respectto the first aspect, the user equipment sends a scheduling requestrequesting resources for uplink transmissions of the buffer statusreport and/or uplink user data. The scheduling request may betransmitted by using statically assigned resources of the PUCCH (D-SR).Instead of monitoring the downlink control channel for the correspondinguplink grant from the base station immediately upon transmitting thededicated scheduling request, it is advantageous to delay the monitoringfor a particular time, such that the user equipment only startsmonitoring the downlink control channel after a particular amount oftime has passed. Considering that the dedicated scheduling request needsto be transmitted over the radio link, needs to be processed at the basestation and the base station needs to transmit the corresponding uplinkgrant over the radio link back to the user equipment, the monitoring ofthe downlink control channel (i.e., PDCCH) can be deferred by some timewithout running the risk of “missing” the downlink control channel(PDCCH) with the uplink grant. A possible delay may be, e.g., 3subframes, but may also be configured to be less or more than that.

The advantage provided by this second aspect is that the user equipmentdoes not need to be awake after sending the dedicated scheduling requestand before starting to monitor the downlink control channel, therebysaving power.

Additionally, the monitoring of the downlink control channel can beeither stopped when receiving the corresponding downlink control channelwith the uplink grant or can be stopped before by setting a timer, whichis used to stop the downlink control channel monitoring by the userequipment even if no uplink grant is received.

According to a third aspect which can be used in combination orindependent from the above first and second aspects, the retransmissionprotocol employed between the user equipment and the base station isimproved by defining that receiving an acknowledgement via a downlinkfeedback channel from the base station without a corresponding downlinkcontrol channel will trigger the user equipment to stop monitoring thedownlink control channel. In more detail, a retransmission or feedbackprotocol is used by the user equipment and the base station tonegatively or positively acknowledge an uplink transmission by the userequipment. A downlink feedback channel is used to transport thenegative/positive acknowledgement to the user equipment, and the userequipment accordingly monitors same to receive the acknowledgement,every time after it transmits uplink data.

In addition, the user equipment monitors the downlink control channelfor a retransmission request sent by the base station, in case the basestation requests the user equipment to retransmit a previous uplinktransmission of data. The instruction over the downlink control channeland the acknowledgement via the downlink feedback channel do not need tocoincide; for example, the downlink control channel might instruct theuser equipment to retransmit data, even though the downlink feedbackchannel transported a positive acknowledgement. In those cases, theinstruction from the downlink control channel overwrites the indicationfrom the downlink feedback channel. However, up to now, when the userequipment receives a positive acknowledgement from the base station,without receiving a corresponding instruction via the downlink controlchannel, the user equipment does not perform a retransmission or newtransmission, but keeps the data in the buffer of the retransmissionprotocol while further monitoring the downlink control channel forfurther instructions over the downlink control channel.

According to this third aspect, when the user equipment receives apositive acknowledgement regarding previously transmitted data withoutreceiving a corresponding downlink control channel, it stops monitoringthe downlink control channel for further instructions. This reduces theactive time of the user equipment thus allowing to further reduce thepower usage.

A fourth aspect, which can be used in combination or independent fromthe above first, second and third aspects, introduces a scheme to allowrestricting the use of dedicated scheduling request resources dependingon the priority or kind of data triggering the corresponding schedulingrequest. As explained before, static resources of an uplink controlchannel are available to the user equipment to transmit the schedulingrequest via the uplink control channel; they may be termed dedicatedscheduling request resources. The dedicated scheduling request resourcesare periodic in time. Scheduling requests are indirectly triggered bydata arriving in a transmission buffer, as explained in detail before.The data belongs to a logical channel which is associated with aparticular priority; thus, the scheduling request can be said to have apriority too, namely the priority of the data which triggered thescheduling request.

According to the fourth aspect, the periodic dedicated schedulingrequest resources are assigned a priority threshold restricting the useof said particular resource to only those scheduling requests that havea high enough priority. In particular, preferably if the priority of thescheduling request surpasses (or at least equals) the priority thresholdrequired for the dedicated scheduling request resource, the userequipment can actually use said resource to transmit the schedulingrequest. In case the priority of the scheduling request does not exceed(or equal) the priority threshold for the dedicated resource, the userequipment needs to wait for the next dedicated scheduling requestresource and again compare the scheduling request priority against therequired priority threshold of the dedicated scheduling requestresource. Correspondingly, there are defined dedicated schedulingrequest resources that can be used for both low and high priorityscheduling requests, as well as other dedicated scheduling requestresources that are restricted to high priority scheduling requests only.

One implementation of the fourth aspect defines two (or more) cycles forthese dedicated scheduling request resources. The first cycle may referto a, e.g., low required priority, and the second cycle may refer to a,e.g., high required priority. Every n-th periodic resource is assignedto the first low-priority cycle, every m-th periodic resource isassigned to the second high-priority cycle.

Preferably, every dedicated scheduling request resource should be usablefor high priority scheduling requests, such that the second cycle may bebasically the cycle of the dedicated scheduling request resource itself.On the other hand, not every periodic resource shall be usable for lowpriority scheduling requests, such that the scheduling requests for lowpriority data are postponed until a corresponding periodic resource ofthe first cycle.

A variation of the fourth aspect assumes that scheduling requests arenot only transmitted via the primary cell of the system, but may also betransmitted using a secondary cell of the system. Periodic dedicatedscheduling request resources are defined for the primary as well as thesecondary cell, usable by the user equipment to transmit a schedulingrequest. In this variation the periodic resources of the primary cellmay only be used for transmitting a scheduling request triggered by highpriority data (i.e., exceeding or at least equaling a correspondingpredetermined priority threshold assigned to the primary cell's periodicdedicated scheduling request resources). Conversely, the dedicatedresources of the secondary cell may be used for transmitting schedulingrequests triggered by low priority data; of course, these resourcesmight also be used for high priority scheduling requests if necessary.

Another variation differentiates between the kind of data that triggersthe scheduling request, e.g., between control and user data. In thiscase, the dedicated scheduling request resources of the primary cell mayonly be used for transmitting a scheduling request triggered by controldata, whereas the dedicated resources of the secondary cell may be usedmainly for transmitting a scheduling request triggered by user data.

The present invention provides a method for requesting resources by auser equipment in a communication system, wherein the user equipmentcomprises a transmission buffer for temporarily storing data to betransmitted in the uplink to a radio base station. A first triggercondition and a second trigger condition are defined, the first triggercondition requiring arrival of new data in the transmission buffer, andthe second trigger condition requiring a value associated with the datain the transmission buffer to exceed a predetermined threshold value.The user equipment determines whether the first trigger condition isfulfilled. When the first trigger condition is fulfilled, the userequipment determines whether the second trigger condition is fulfilled.The user equipment transmits a scheduling request to the radio basestation for requesting uplink resources, in case it is determined thatthe second trigger condition is fulfilled.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the first and secondtrigger conditions are defined for triggering the transmission of abuffer status report; the triggering of the buffer status reporttriggers a transmission of the scheduling request in case no uplinkresources are available for the user equipment to transmit the bufferstatus report.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the second triggercondition requires that the amount of data in the transmission bufferexceeds the predetermined threshold value, or requires that the time thedata is in the transmission buffer exceeds the predetermined thresholdvalue.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the first triggercondition requires: new data to arrive in the transmission buffer, whenthe transmission buffer is empty, or new data to arrive in thetransmission buffer and this new data to be of higher priority than dataalready in the transmission buffer, when the transmission buffer is notempty. The user equipment stores that the first trigger condition isfulfilled, upon determining that new data arrived in the emptytransmission buffer.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, a plurality of logicalchannels are configured for the user equipment, and one transmissionbuffer is provided in the user equipment for each logical channel. Thedetermining of whether the second trigger condition is fulfilled is onlyperformed for at least one out of the plurality of logical channels. Inan advantageous embodiment this is done for a logical channel associatedwith data of low priority.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, a plurality of logicalchannels are configured for the user equipment, and one transmissionbuffer is provided in the user equipment for each logical channel. Thedetermining of whether the second trigger condition is fulfilled is onlyperformed for at least one out of different logical channel groups intowhich the plurality of logical channels are grouped. In an advantageousembodiment this is done for a logical channel group associated with dataof low priority. The second trigger condition requires that the sum ofdata in the transmission buffers of the logical channels of the logicalchannel group exceeds the predetermined threshold value.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the scheduling requestis transmitted from the user equipment to the radio base station in aresource of an uplink control channel or via a random access procedure.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the predeterminedthreshold value is predetermined by the user equipment. In anadvantageous embodiment, this is done based on stored traffic historydata, and the user equipment transmits the predetermined threshold valueto the radio base station. Alternatively, the predetermined thresholdvalue is predetermined by a node of the communication system other thanthe user equipment, advantageously based on traffic history datareceived from the user equipment.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the user equipmentreceives an uplink grant message from the radio base station, includinginformation on uplink resources allocated to the user equipment by theradio base station. The user equipment transmits a buffer status report,and optionally at least part of the data in the transmission buffer, tothe radio base station, using the allocated uplink resources included inthe uplink grant message.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the user equipmentmonitors a downlink control channel, and starts monitoring the downlinkcontrol channel a predetermined time after transmitting the schedulingrequest to the radio base station. In an advantageous embodiment, themonitoring is performed until either the user equipments receives anuplink grant message via the downlink control channel or a secondpredetermined time after transmitting the scheduling request expires.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the user equipmenttransmits data to the radio base station, and monitors a downlinkfeedback channel for a positive or negative acknowledgment message fromthe radio base station, after transmitting the data to the radio basestation. The user equipment further monitors a downlink control channelfor a retransmission request message from the radio base station, aftertransmitting the data to the radio base station, the retransmissionrequest message requesting the user equipment to retransmit the data.The monitoring of the downlink control channel for the retransmissionrequest message from the radio base station is stopped, when receiving apositive acknowledgment message via the downlink feedback channelwithout receiving the downlink control channel.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, periodic resourcesassociated with an uplink control channel are allocated to the userequipment and are usable by the user equipment to transmit a schedulingrequest to the radio base station. Each of the periodic resourcesassociated with the uplink control channel is assigned a requiredpriority. The triggered scheduling request is assigned a schedulingrequest priority which corresponds to the priority of the data whichtriggered the transmission of the scheduling request. In an advantageousembodiment, the priority of the data corresponds to the priority of thelogical channel associated with said data. Each of said periodicresources is only usable for transmitting scheduling requests with thescheduling request priority being equal to or higher than the requiredpriority of the periodic resource.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the user equipmentdetermines whether the scheduling request priority is equal to or higherthan the required priority of the periodic resource of the uplinkcontrol channel. In case it is determined that the scheduling requestpriority is equal to or higher than the required priority of theperiodic resource, the scheduling request is transmitted using theperiodic resource. In case it is determined that the scheduling requestpriority is not equal to or higher than the required priority of theperiodic resource, the user equipment determines whether the schedulingrequest priority is equal to or higher than the required priority of anext periodic resource of the uplink control channel.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, at least a first andsecond scheduling request cycle are defined for the periodic resourcesof the uplink control channel, such that every n-th periodic resource ofthe uplink control channel is associated with the first schedulingrequest cycle and every m-th periodic resource of the uplink controlchannel is associated with the second scheduling request cycle, wherem≠n. The first scheduling request cycle is assigned a first requiredpriority and the second scheduling request cycle is assigned a secondrequired priority.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, carrier aggregation isused between the user equipment and the base station, with a primarycarrier and a secondary carrier. Periodic resources for the primarycarrier and periodic resources for the secondary carrier are allocatedto the user equipment and are usable by the user equipment to transmit ascheduling request to the radio base station. The periodic resources forthe primary carrier are used for transmitting a scheduling requesttriggered by first kind of data, and the periodic resources for thesecondary carrier are used for transmitting a scheduling requesttriggered by second kind of data.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the first kind of datais data with a priority exceeding a predetermined priority threshold ofthe periodic resources for the primary carrier, and the second kind ofdata is data with a priority equal to or below the predeterminedpriority threshold. Alternatively, the first kind of data is controlplane data, and the second kind of data is user plane data.

The present invention further provides a user equipment for requestingresources in a communication system. A transmission buffer of the userequipment temporarily stores data to be transmitted in the uplink to aradio base station. A memory of the user equipment stores a firsttrigger condition and a second trigger condition, the first triggercondition requiring the arrival of new data in the transmission buffer,and the second trigger condition requiring a value associated with thedata in the transmission buffer to exceed a predetermined thresholdvalue. A processor of the user equipment determines whether the firsttrigger condition is fulfilled. The processor further determines whetherthe second trigger condition is fulfilled, when the first triggercondition is fulfilled. A transmitter of the user equipment transmits ascheduling request to the radio base station for requesting uplinkresources, in case the processor determined that the second triggercondition is fulfilled.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the first and secondtrigger conditions are defined for triggering the transmission of abuffer status report. The triggering of the buffer status reporttriggers the transmission of the scheduling request in case no uplinkresources are available for the user equipment to transmit the bufferstatus report.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the second triggerconditions requires:

-   -   the amount of data in the transmission buffer exceeds the        predetermined threshold value, or    -   the time the data is in the transmission buffer exceeds the        predetermined threshold value.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the first triggercondition requires:

-   -   new data to arrive in the transmission buffer, when the        transmission buffer is empty, or    -   new data to arrive in the transmission buffer and this new data        to be of higher priority than data already in the transmission        buffer, when the transmission buffer is not empty.

The memory further stores that the first trigger condition is fulfilled,upon the processor determined that new data arrived in the emptytransmission buffer.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, a plurality of logicalchannels are configured for the user equipment, and the user equipmentcomprises one transmission buffer for each logical channel. Theprocessor performs the determination of whether the second triggercondition is fulfilled for only at least one out of the plurality oflogical channels. In an advantageous embodiment this is done for alogical channels associated data of low priority.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, a plurality of logicalchannels are configured for the user equipment, and one transmissionbuffer is provided in the user equipment for each logical channel. Theprocessor performs the determination of whether the second triggercondition is fulfilled only for at least one out of different logicalchannel groups, into which the plurality of logical channels aregrouped. In an advantageous embodiment this is done for a logicalchannel group associated with data of low priority. The processorcalculates the sum of data in the transmission buffers of the logicalchannels of the logical channel group, and determines when thecalculated data sum exceeds the predetermined threshold value.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the transmitter isadapted to transmit the scheduling request to the radio base station ina resource of an uplink control channel or via a random accessprocedure.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the processorpredetermines the predetermined threshold value. In an advantageousembodiment this is done based on stored traffic history data, and thetransmitter is preferably adapted to transmit the predeterminedthreshold value to the radio base station. The transmitter transmitsstored traffic history data to a network entity that predetermines thepredetermined threshold value, and a receiver of the user equipmentreceives the predetermined threshold value from said network entity.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, a receiver receives anuplink grant message from the radio base station, including informationon uplink resources allocated to the user equipment by the radio basestation. The transmitter transmits a buffer status report, andoptionally at least part of the data in the transmission buffer, to theradio base station, using the allocated uplink resources included in theuplink grant message.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, a monitoring circuitmonitors a downlink control channel and starts monitoring the downlinkcontrol channel a predetermined time after transmitting the schedulingrequest to the radio base station. In an advantageous embodiment, themonitoring circuit monitors the downlink control channel until eitherthe user equipment receives an uplink grant message via the downlinkcontrol channel or a second predetermined time after transmitting thescheduling request expires.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the transmittertransmits data to the radio base station. A monitoring circuit monitorsa downlink feedback channel for a positive or a negative acknowledgementmessage from the radio base station, after transmitting the data to theradio base station. The monitoring circuit monitors a downlink controlchannel for a retransmission request message from the radio basestation, after transmitting the data to the radio base station, theretransmission request message requesting the user equipment toretransmit the data. The monitoring circuit stops the monitoring of thedownlink control channel, when receiving a positive acknowledgmentmessage via the downlink feedback channel without receiving the downlinkcontrol channel.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, periodic resourcesassociated with an uplink control channel are allocated to the userequipment and are usable to transmit a scheduling request to the radiobase station. Each of the periodic resources associated with the uplinkcontrol channel is assigned a required priority, and wherein thetriggered scheduling request is assigned a scheduling request priority,which corresponds to the priority of the data that triggered thetransmission of the scheduling request, and preferably the priority ofthe data corresponds to the priority of the logical channel associatedwith said data. Each of said periodic resources is only usable fortransmitting scheduling requests with the scheduling request prioritybeing equal to or higher than the required priority of the periodicresource.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the processor determineswhether the scheduling request priority is equal to or higher than therequired priority of the periodic resource of the uplink controlchannel. In case it is determined that the scheduling request priorityis equal to or higher than the required priority of the periodicresource, the scheduling request is transmitted using that resource. Incase it is determined that the scheduling request priority is not equalto or higher than the required priority of the periodic resource, theprocessor determines whether the scheduling request priority is equal toor higher than the required priority of a next periodic resource of theuplink control channel.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, at least a first andsecond scheduling request cycle are defined for the periodic resourcesof the uplink control channel, such that every n-th periodic resource ofthe uplink control channel is associated with the first schedulingrequest cycle, and every m-th periodic resource of the uplink controlchannel is associated with the second scheduling request cycle, wherem≠n. The first scheduling request cycle is assigned a first requiredpriority and the second scheduling request cycle is assigned a secondrequired priority.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, carrier aggregation isused between the user equipment and the base station, with a primarycarrier and a secondary carrier. Periodic resources for the primarycarrier and periodic resources for the secondary carrier are allocatedto the user equipment and are usable by the user equipment to transmit ascheduling request to the radio base station. The periodic resources forthe primary carrier are used for transmitting a scheduling requesttriggered by first kind of data, and the periodic resources for thesecondary carrier are used for transmitting a scheduling requesttriggered by second kind of data.

According to an advantageous embodiment of the invention which can beused in addition or alternatively to the above, the first kind of datais data with a priority exceeding a predetermined priority threshold ofthe periodic resources for the primary carrier, and the second kind ofdata is data with a priority equal to or below the predeterminedpriority threshold. Alternatively, the first kind of data is controlplane data, and the second kind of data is user plane data.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary overview of the overall E-UTRAN architectureof 3GPP LTE,

FIG. 3 shows exemplary subframe boundaries on a downlink componentcarrier as defined for 3GPP LTE (Release 8/9),

FIG. 4 shows an exemplary downlink resource grid of a downlink slot asdefined for 3GPP LTE (Release 8/9),

FIGS. 5 and 6 show the 3GPP LTE-A (Release 10) Layer 2 structure withactivated carrier aggregation for the downlink and uplink, respectively,

FIG. 7 shows a state diagram for a mobile terminal and in particular thestates RRC_CONNECTED and RRC_IDLE and the functions to be performed bythe mobile terminal in these states,

FIG. 8 illustrates the DRX operation of a mobile terminal, and inparticular the DRX opportunity, on-duration, according to the short andlong DRX cycle,

FIG. 9 illustrates the resource request procedure between the userequipment and the base station in view of the transmission bufferstatus, according to the prior art,

FIG. 10 illustrates the improved resource request procedure between theuser equipment and the base station according to the first embodiment ofthe invention,

FIGS. 11 and 12 illustrate the process in the user equipment for theimproved resource request procedure according to variants of the firstembodiment of the invention,

FIG. 13 illustrates the process in the user equipment for the improvedresource request procedure according to a more detailed first embodimentof the invention,

FIG. 14 illustrates the shortened time window for PDCCH monitoring bythe UE according to a second embodiment of the invention,

FIG. 15 illustrates the prioritization of dedicated scheduling requestresources for transmitting scheduling requests according to a fourthembodiment of the invention, and

FIG. 16 illustrates a variant of the fourth embodiment of the invention,in which dedicated scheduling request resources of a PCell and a SCellare assigned different required priorities.

DETAILED DESCRIPTION OF THE INVENTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to a radio access scheme according to 3GPP LTE(Release 8/9) and LTE-A (Release 10/11) mobile communication systems,partly discussed in the Technical Background section above. It should benoted that the invention may be advantageously used for example in amobile communication system such as 3GPP LTE-A (Release 10/11)communication systems as described in the Technical Background sectionabove, but the invention is not limited to its use in this particularexemplary communication networks.

The term “new data” used in the claims and in the description is to beunderstood as data that arrives/is stored in the transmission bufferwhich was previously not there. This data (data packets) is receivedfrom a higher layer, e.g., PDCP layer, and placed into the transmissionbuffer. This term is used in contrast to “old data”, referring to datawhich is kept in the transmission buffer as long as the retransmissionprotocol makes sure that this data is correctly received at thereceiving side.

The terms “exceed” or “surpass” used in the claims and in thedescription in connection with thresholds shall not be usedrestrictively to mean that the threshold needs to be actually exceeded(i.e., higher than), but may also encompass that the threshold isequaled (i.e., is the same as).

The term “arrival” used in the claims and in the description with regardto data and transmission buffers shall be understood as that data whichis to be transmitted by the user equipment “enters”, or “is put into”,or “is temporarily stored in” the transmission buffer of thecorresponding logical channel for transmission.

In the following, several embodiments of the invention will be explainedin detail. The explanations should not be understood as limiting theinvention, but as a mere example of the invention's embodiments tobetter understand the invention. A skilled person should be aware thatthe general principles of the invention as laid out in the claims can beapplied to different scenarios and in ways that are not explicitlydescribed herein. Correspondingly, the following scenario assumed forexplanatory purposes of the various embodiments shall not limit theinvention as such.

A user equipment is provided with transmission buffer memory for eachlogical channel, used for temporarily storing uplink data until it issuccessfully transmitted over the radio link to the eNodeB. Furthermore,the UE has no resources available to transmit the data or a bufferstatus report to the base station, making it thus necessary to perform ascheduling request with the eNB, which process shall be improved by thefirst embodiment of the invention.

As explained before, scheduling requests may be either transmitted viaresources of the PUCCH allocated by the eNB or by using a RACHprocedure. If not indicated differently, in the following we will assumethat such resources of the PUCCH, which are typically allocatedperiodically by the eNB, are available to the UE for transmitting thescheduling request as soon as it is triggered; nevertheless, theinvention is also applicable when using a RACH procedure instead. Ascheduling request is usually one bit long, and corresponding periodicPUCCH resources allow transmitting the scheduling request but are notsufficient for transmitting further data such as the buffer statusreport or actual data of the transmission buffer.

A first embodiment of the invention will be explained in connection withFIG. 10, which illustrates the transmission buffer at the user equipmentand the messages exchanged with the base station to request resourcesand transmit the buffer status report, the scheduling request and data.FIG. 11 illustrates the process at the user equipment for performing thefirst embodiment of the invention where the second trigger conditionrequires a data quantity threshold to be exceeded; FIG. 12 is analternative to FIG. 11 and illustrates the process at the user equipmentfor performing the first embodiment of the invention where the secondtrigger condition requires a timer to expire. FIG. 13 also illustratesthe process at the user equipment for performing the first embodiment ofthe invention but is more detailed than FIG. 11.

The main idea in this first embodiment is to delay the triggering of thebuffer status report/scheduling request compared to the standardtriggering procedure as explained in the Background Section inconnection with FIG. 9. Postponing the buffer status report/schedulingrequest allows that more data arrives in the transmission buffer, andthus uplink transmissions transport more data in less time.Correspondingly, the triggering of the buffer status report/schedulingrequest is performed when sufficient data is in the transmission buffer(i.e., more than some predetermined threshold), and not immediately whennew data arrives in the empty transmission buffer. It is more powerefficient to transmit larger Transport Block sizes, rather thantransmitting smaller Transport Block sizes. Also, the PDCCH load isdecreased significantly as will be explained.

As in the prior art, a buffer status report may be triggered first,immediately followed by the triggering of a scheduling request providedno uplink resources are available to transmit the triggered bufferstatus report.

The first embodiment of the invention may be implemented in thefollowing exemplary way. The triggering of a scheduling request in theuser equipment depends on two conditions, which shall be both fulfilled.Both trigger conditions in the context of an LTE implementation relateto the transmission of a buffer status report, which however directlyleads to a transmission of a scheduling request, since it is assumedthat no resources are available for the user equipment to transmit thetriggered buffer status report; thus, it can be also said that thetrigger conditions are defined for the transmission of the schedulingrequest too.

The first trigger condition requires new data to become available in thetransmission buffer, which means that data from higher layers shall betransmitted in the uplink to the base station and is thus entered intothe transmission buffer of the user equipment. It should be noted thatthe first trigger condition is fulfilled independent from whether thetransmission buffer is empty or not and independent from the priority ofthe new data, as long as new data becomes available in the transmissionbuffer. A variant of this first trigger condition will be explainedlater, which advantageously reuses the trigger condition for the bufferstatus report as currently used in the 3GPP standardization and asexplained in this Background Section.

This is depicted in FIGS. 11 and 13, where the user equipment checkswhether new data arrives in its transmission buffer.

The second trigger condition is basically responsible for postponing thetriggering of the scheduling request; it requires that there is enoughdata in the transmission buffer or that the data be in the transmissionbuffer for at least a specific amount of time. Correspondingly, the datain the transmission buffer shall in general surpass a predeterminedthreshold, be it an amount of data or a period of time. The triggeringof the scheduling request becomes thus threshold-based according to thisfirst embodiment.

For the second trigger condition the user equipment checks for examplewhether the amount of data in the transmission buffer is at least equalto or higher than a predetermined data quantity threshold.

In FIGS. 11 and 13 it is assumed that the user equipment checks thesecond trigger condition requiring the amount of data to exceed athreshold, i.e., be equal to or higher than the threshold. Though itappears logical to check the first and second trigger condition in theorder as illustrated in FIGS. 11 and 13, i.e., first the first triggercondition and then the second trigger condition, this is not necessary.The user equipment may also first check the second trigger condition andthen the first trigger condition.

It should be also noted that if the second trigger condition (requiringthe data amount to surpass a data quality threshold) is fulfilled, thisautomatically requires that the first trigger condition is fulfilled. Inother words, the amount of data in the transmission buffer can only thensuddenly exceed a predetermined data amount, if new data arrives in thetransmission buffer, which corresponds to the requirement of the firsttrigger condition. Thus, in one alternative of the first embodiment, thefirst trigger condition does not necessarily need to be checked for thefirst embodiment; it suffices to check only the second trigger conditionsuch that the BSR/SR is triggered when the amount of data in thetransmission buffer exceeds a certain threshold.

Alternatively, instead of the data quantity threshold as the secondtrigger condition, the user equipment starts a timer with apredetermined time length when data arrives in the empty transmissionbuffer. This alternative is depicted in FIG. 12. The timer is notstarted every time new data becomes available at the transmissionbuffer, but only for the first time when the data enters an emptytransmission buffer. Then, when the thus started timer related to thedata of the transmission buffer expires, the user equipment considersthe second trigger condition to be true.

In contrast to the other variant of the second trigger condition (seeFIGS. 11 and 13), in case a timer is used as the second triggercondition, the first trigger condition does not necessarily need to befulfilled when the second trigger condition is fulfilled.Correspondingly, the fact that the first trigger condition is true maybe stored in the user equipment as long as necessary, i.e., as long asit checks for the second trigger condition. On the other hand, if thetimer for the second trigger condition is started when the userequipment determines for the first time that the first trigger conditionis fulfilled, the storing of the fulfilled first trigger condition isimplicit in the running of the timer; a separate storage in said respectis then not necessary.

According to still further variants of the first embodiment, the firsttrigger condition may correspond to the one that is currently employedin the 3GPP standard and explained in the background section. Inparticular, the first trigger condition might thus require that new dataarrives in an empty transmission buffer, or that the new data arrivingin a non-empty transmission buffer has a higher priority than the dataalready stored in the non-empty transmission buffer (compare to TS36.321 v10.5.0 5.4.5). It should be noted that the first triggercondition according to standard definition would not be fulfilled fordata arriving in a non-empty transmission buffer, since said newlyarrived data might not have a higher priority but most likely the samepriority as that data already in the transmission buffer. Accordingly,the first trigger condition would only become true when new data arrivesin the empty transmission buffer; this first trigger condition becomingtrue shall be stored for as long as necessary, e.g., while determiningwhether the second trigger condition is fulfilled. Alternatively, whenthe second trigger condition is the timer (see above) and the timer isstarted when the first trigger condition is fulfilled, a separatestoring of the fulfilled first trigger condition might not be necessary.Also, when the second trigger condition refers to the data quantitythreshold, the check for the first trigger condition might be skipped,for basically the same reasons as explained before

Correspondingly, when the trigger conditions for transmitting ascheduling request are fulfilled as explained above according to one ofthe variants of the first embodiment, the scheduling request istransmitted from the user equipment to the base station. FIG. 13 is morespecific in that it illustrates that the above described triggerconditions are checked in order to determine whether to transmit abuffer status report, and that a scheduling request is transmitted whenthe user equipment additionally determines that resources are notavailable for transmission of the buffer status report.

FIG. 10 illustrates that the SR is not transmitted when new data arrivesin the empty transmission buffer at time t1 or new data arrives in thetransmission buffer at time t2. At time t1 and t2 the first triggercondition according to FIG. 11 or FIG. 13 is fulfilled, but the secondtrigger condition is not fulfilled yet, since the total amount of datain the transmission buffer remains below the threshold (dashed line inFIG. 10). Only at time t3, the first and the second trigger conditionsare fulfilled, which thus triggers in the user equipment a transmissionof the scheduling request to the base station. The scheduling request istriggered once, i.e., being a one-shot trigger.

The scheduling request may be transmitted using one of the periodicPUCCH resources, or using a RACH procedure as already indicated before.The scheduling request is usually one bit indicating to the base stationthat resources for an uplink transmission are needed. The base stationreceives and processes the scheduling request, and depending on thecurrent radio conditions, allocates more or less uplink resources to theuser equipment.

The base station correspondingly transmits an uplink grant to the userequipment using the PDCCH, indicating the allocated uplink resources tothe user equipment.

The user equipment monitoring the PDCCH, receives the PDCCH with theuplink grant, and can thus prepare the buffer status report fortransmission to the eNodeB. Depending on how much resources wereallocated to the user equipment, not only the buffer status report maybe sent but also part of the data in the transmission buffer; in thatcase, the buffer status report only indicates the remaining amount ofdata in the transmission buffer, i.e., without the data that fits in thefirst-allocated resources.

The buffer status report and possibly part of the uplink data aretransmitted by the user equipment to the eNodeB on the PUSCH. In turn,the eNodeB can allocate further resources to the user equipment, thusallowing the user equipment to empty the transmission buffer asillustrated at times t4, t5 and t6. FIG. 10 assumes a dynamic allocationof uplink resources by the eNodeB (for each subframe a separate uplinkgrant); however, although not illustrated, a semi-persistent allocationof uplink resources would also be possible, such that the user equipmentreceives an uplink grant allocating periodic resources in the uplinkwhich may be used by the user equipment to empty the transmission bufferand transmit the data to the eNodeB.

FIG. 10 assumes that three uplink transmissions are sufficient to emptythe transmission buffer; however, this is only an example and more orless transmissions may be needed.

The advantages provided by the first embodiment will be explained in thefollowing. From transmission power perspective it is better to transmitlarger Transport Block Sizes in a short time, rather than transmittingsmaller Transport Block sizes more often. Correspondingly, the dataquantity threshold used as the second trigger condition can be definedsuch that the data of the transmission buffer fits a large transportblock size.

The user equipment transmits the scheduling request less often, and as aresult, the UE also needs to monitor less often the PDCCH for uplinkgrants, such that the DRX period of the user equipment may be longer andless power is needed. It should be noted that the transmission power isnot only decreased due to less PUCCH transmissions (D-SR) and PUSCHtransmissions, but also due to the fact that the “Active Time” isshortened. When comparing the scheduling request procedure of FIG. 9(prior art) with that of FIG. 10 (invention), the PDCCH load isdecreased significantly, in this example by a factor of 3.

The above-explained buffer status report/scheduling request triggeringmay be implemented in the LTE system as explained in the backgroundsection. The first and second trigger conditions shall replace or extendthe buffer status request triggering of the prior art. For example, the3GPP standard trigger (more in particular the first trigger conditionwhich requires that new data arrives in an empty transmission buffer, orthat the new data arriving in a non-empty transmission buffer has ahigher priority than the data already stored in the non-emptytransmission buffer) may be disabled and replaced by the new triggers ofthis first embodiment.

The trigger definition for triggering the transmission of a bufferstatus report to be employed in the 3GPP standard of LTE could beaccording to one variant of the first embodiment:

-   -   When new data arrives in the buffer for a logical channel, and        the amount of data for this logical channel is above a        predefined threshold

Up to now, the transmission buffer and buffer status report/schedulingrequest triggering has been explained for the user equipment in general.Nevertheless, the above described first embodiment may be applicable toonly one or more of the various configured logical channels; for theremaining logical channels, the old trigger according to 3GPP standardwould be used in this case. The logical channel for which theabove-described improved scheduling request triggering of the firstembodiment is applied may refer to services having no demanding QoSrequirements (e.g., in terms of delay) like voice as for example lowvolume background services or Instant messaging traffic or specific MTCservices for gas metering or animal, cargo, prisoner, elderly andchildren tracking. For such services the invention described in thevarious embodiments provides mechanisms allowing an efficient use ofradio resources, UE power resources and network resources.

Logical channels in a user equipment are grouped in logical channelgroups by the eNodeB, depending, e.g., on the QoS requirements of eachlogical channel. Correspondingly, the above-described first embodimentmay be applicable to one or more of the defined logical channel groups(four in total, at the moment); for the remaining logical channelgroups, the old trigger according to 3GPP standard would be used in thiscase. In particular, when considering whole logical channel groups, thefirst trigger condition and second trigger condition of the firstembodiment shall also apply to a whole logical channel group todetermine whether to transmit a buffer status report, i.e., a schedulingrequest, to the eNodeB. Particularly, the first trigger condition isfulfilled when new data arrives in a transmission buffer of any of thelogical channels of a logical channel group. The second triggercondition is fulfilled when the data in the transmission buffers of allthe logical channels of a logical channel group (i.e., a sum of alltransmission buffer data in a LCG) exceeds a threshold (be it a timer ordata quantity threshold).

The particular thresholds used for the second trigger condition may beset by the network or the user equipment; being predefined by thenetwork, gives the network full control over the scheduling relatedsignaling procedures. Advantageously, the user equipment, having moreinformation regarding the traffic statistics running in the uplink, mayassist the network in defining a suitable threshold by transmittingappropriate data to the network. Alternatively, the user equipment usesthe traffic statistics to select a threshold on its own, and thus mayalso consider its power management requirements; then, the userequipment may or may not inform the network about the selected threshold

Further Embodiments

In the following, second, third and fourth embodiments are described,which can be used in addition to each other embodiment, or may be usedindependent from each other embodiment.

According to a second embodiment of the invention, the active time ofthe user equipment for monitoring the PDCCH is shortened in order toreduce its battery consumption. Please note that the second embodimentmainly relates to the scheduling request transmitted via the periodicresources of the PUCCH, but not to the scheduling request beingtransmitted via the RACH procedure. In particular, after transmitting adedicated scheduling request to the eNodeB, the user equipment needs tomonitor the PDCCH for the uplink grant, which the eNodeB sends inresponse to the scheduling request.

The user equipment behavior currently specified in the 3GPP standard isthat the user equipment starts monitoring the PDCCH immediately aftersending the dedicated scheduling request; the user equipment is thus inactive time beginning from the subframe where the scheduling request istransmitted until the corresponding uplink grant is received. Dependingon the eNodeB response, the active time could include potentialretransmissions of the scheduling request due to previous transmissionerrors, and thus become quite long. This is not power efficient.

In view of the time needed for the scheduling request and then later theuplink grant to travel over the radio link, and the time needed for theeNodeB to process the scheduling request and to generate and transmitthe uplink grant message, in the second embodiment of the invention, thetime window for monitoring the PDCCH is shortened, as explained inconnection with FIG. 14. A time delay is introduced after sending thescheduling request, such that the user equipment starts monitoring thePDCCH for the uplink grant only after the time delay, i.e., after apredetermined amount of time has expired. The transmission of thescheduling request could start a timer, upon which expiry the userequipment starts the PDCCH monitoring. As an example, 3 subframes couldbe used as the delay after the dedicated scheduling requesttransmission.

Furthermore, the PDCCH monitoring may be also stopped after a particularperiod of time, even if no uplink grant is received; thus, another timermay be running while monitoring the PDCCH, and when the timer expires,the PDCCH monitoring is stopped by the UE. The timer can be started whentransmitting the D-SR or when the PDCCH monitoring is started.

Thus, by postponing the start of the PDCCH monitoring in the userequipment, and possibly canceling the PDCCH monitoring ahead ofreceiving the uplink grant, the user equipment is less in Active Timeand thus can save power.

The third embodiment of the invention aims at reducing the active timeof a user equipment with respect to uplink data retransmissions. Theuplink retransmission protocol, HARQ, used currently in the prior art asstandardized by 3GPP, is defined such that there are two kind ofretransmissions: non-adaptive and adaptive retransmissions. In general,HARQ schemes can be categorized as either synchronous or asynchronous,with the retransmissions being in each case either adaptive ornon-adaptive. In an adaptive HARQ scheme transmission attributes such asthe modulation and coding scheme, and transmission resource allocationin the frequency domain, can be changed at each retransmission inresponse to variation in the radio channel conditions. In a non-adaptiveHARQ scheme the retransmissions are performed without explicit signalingof new transmission attributes—either by using the same transmissionattributes as those of the previous transmission, or by changing theattributes according to a predefined rule.

A Physical HARQ Indicator CHannel (PHICH) carrying ACK/NACK message foran uplink data transmission may be transmitted at the same time as aPDCCH for the same user equipment. In case of simultaneous transmissionof PHICH and PDCCH, the user equipment follows the indication of thePDCCH; in other words, the indication of the PDCCH overwrites theindication of the PHICH of the same subframe. Correspondingly, the userequipment performs either a transmission of new data or a retransmission(being adaptive), regardless of the PHICH content. When no PDCCH for theuser equipment is detected, the PHICH content dictates the HARQ behaviorof the user equipment.

The currently-used definition of ACK/NACK of the PHICH in the prior artis as follows:

NACK: the terminal performs a non-adaptive retransmission

ACK: the terminal does not perform any uplink retransmission, but keepsthe data in the HARQ buffer for the corresponding HARQ process. Afurther transmission for that HARQ process needs to be explicitlyscheduled by a subsequent grant by the PDCCH; until reception of suchgrant, the terminal is in a “Suspension State”.

The following table gives an overview:

HARQ feedback seen by the UE PDCCH seen (PHICH) by the UE UE behaviorACK or NACK New New transmission according to Transmission PDCCH ACK orNACK Retransmission Retransmission according to PDCCH (adaptiveretransmission) ACK None No (re)transmission, keep data in HARQ bufferand a PDDCH is required to resume retransmissions NACK None Non-adaptiveretransmission

The currently specified user equipment behavior with regard to PHICH andPDCCH thus leads to the situation and problem that, when the userequipment receives an ACK, it means that the user equipment should keepthe data packet (Transport Block) in the transmission buffer of the HARQprocess and monitor at the new HARQ retransmission occasions for aPDCCH. The user equipment has thus to monitor the PDCCH for furtherpotential retransmissions until the maximum number of HARQ transmissionsis exceeded. This requires a lot of power in the user equipment.

According to this third embodiment, the retransmission protocol isimproved by redefining the user equipment behavior regarding the ACK viaPHICH. In particular, when the user equipment receives an ACK via PHICHwithout receiving any PDCCH at the same time (i.e., in the samesubframe), it stops monitoring the PDCCH for further HARQretransmissions. Also, the HARQ buffer is emptied after receiving theACK.

In a variation of this third embodiment, the user equipment behavior isonly changed for specific configured logical channels (or logicalchannel groups), i.e., only in case a transport block contains data ofsuch a configured logical channel (group).

This reduces the active time further and hence reduces battery drain atthe user equipment.

A fourth embodiment of the invention introduces a scheme for restrictingthe use of dedicated scheduling request resources to allowpower-efficient SR reporting. As explained before various times,dedicated resources on the PUCCH are available to the user equipment totransmit a scheduling request; the dedicated scheduling requestresources being periodically allocated by the eNodeB. For example, thesededicated resources of the PUCCH can be assigned a required threshold,which the scheduling request has to “fulfill” in order that the userequipment can transmit the scheduling request using that dedicatedresource; otherwise, a later one of the dedicated resources needs to beused (provided the required priority allows it).

In more detail, each dedicated scheduling request resource is assigned arequired priority, and each scheduling request to be transmitted by theuser equipment is associated with a scheduling request priority. Therequired priority assigned to a particular dedicated resource can bedetermined by the network or by the user equipment, and is preferably inthe form of a priority threshold. The scheduling request priority can bethen defined by the priority of the logical channel which data triggeredthe scheduling request. The priority of a logical channel can be between1 and 8, currently.

Correspondingly, when the transmission of a scheduling request istriggered in the user equipment, the user equipment will compare thescheduling request priority against the priority of the currentlyavailable dedicated resource of the PUCCH, so as to determine whether itmay use said resource to transmit the triggered scheduling request. Onlyin case the scheduling request priority is equal to or higher than therequired priority of the resource, the user equipment transmits thescheduling request using said resource. Otherwise, the user equipmentneeds to wait for the next dedicated scheduling request resource andagain perform the comparison of scheduling request priority against thededicated resource priority, until the user equipment is able totransmit the scheduling request in a dedicated resource with a lowenough required priority.

According to one variant of the fourth embodiment, two D-SR cycles aredefined for the user equipment, e.g., a low-priority and a high-priorityD-SR cycle. It should be noted however that also more than two cyclescan be defined, if necessary; in this case, more than one threshold maybe necessary to control access to the different resources.

The low-priority D-SR cycle may or may not be a multiple of thehigh-priority D-SR cycle. Every n-th periodic PUCCH resource may beassociated with the low-priority D-SR cycle, and every m-th periodicPUCCH resource may be associated with the high-priority D-SR cycle. mand n should be different. Preferably, m should be lower than n, suchthat more resources are available to transmit high-priority schedulingrequests than low-priority scheduling requests. In particular, onlyevery, e.g., fourth (low-priority D-SR cycle with n=4) periodic resourceshall be usable for low-priority scheduling requests, while, e.g., everyresource (high-priority D-SR cycle with m=1) shall be usable forhigh-priority scheduling requests. This is depicted in FIG. 15.

As a result, low priority scheduling requests are transmitted less oftencompared to high-priority scheduling requests. The data which triggereda low-priority scheduling request can tolerate more delay, and thereforewill be transmitted less frequently, thereby achieving some benefit interms of battery power. High-priority scheduling requests can betransmitted at every D-SR PUCCH resource in order to fulfill tight delayrequirements.

Alternatively, each logical channel (or logical channel group) can beassigned a particular D-SR cycle, the user equipment shall use forscheduling request triggered by data of said logical channels (orlogical channel group). This association could be done at radio bearerestablishment, when the logical channels are grouped into logicalchannel groups.

According to further variants of the fourth embodiment, the userequipment shall only use one D-SR cycle at a time. In the example ofFIG. 15 this would mean that the user equipment either uses thelow-priority or high-priority D-SR cycle at one time. If a low-priorityscheduling request is to be transmitted, the low-priority D-SR cycle isused. In case a high-priority scheduling request is triggered, the userequipment (when in low-priority D-SR cycle) will switch to thehigh-priority D-SR cycle. At the transition between the D-SR cycles (inboth ways), the SR_counter should be set to 0, and the sr-ProhibitTimershall be stopped.

Another variant of the fourth embodiment will be explained withreference to FIG. 16, illustrating the dedicated scheduling requestresources for a PCell and an SCell. In this variant, it is assumed thatscheduling requests can be transmitted on the PUCCH via the PCell or theSCell. The user equipment uses carrier aggregation to aggregate severalserving cells (component carriers), and the user equipment is allocatedPUCCH resources for the dedicated scheduling request on multiple cells.In the following and for explanatory purposes only, it is assumed thatthe user equipment aggregates a PCell and one SCell; a user equipmentmay have more than one SCell.

The fourth embodiment allows defining usage rules for the D-SR resourcesof the PCell and SCell. In a first variant, the usage of D-SR resourcesof the PCell and SCell is distinguished by the priority of thescheduling request. Correspondingly, the D-SR resources of the PCell areassigned a first required priority (e.g., for high-priority), and theD-SR resources of the SCell are assigned a second required priority(e.g., for low-priority). Thus, the user equipment shall transmitlow-priority scheduling requests preferably via the D-SR resources ofthe SCell, and shall transmit high-priority scheduling requestspreferably via the D-SR resources of the PCell (or if necessary via theD-SR of the SCell).

According to another variant of the fourth embodiment, instead of usingpriorities, the usage of the SCell/PCell D-SR resources might depend onthe kind of data that triggered the scheduling request, e.g., user vscontrol data. In particular, the scheduling request triggered by controlplane data, such as RRC signaling, shall be transmitted via the D-SRresources of the PCell, whereas a scheduling request triggered by userplane data shall be transmitted via the D-SR resources of the SCell. Oneadvantage is that depending on which D-SR resource was used by the userequipment, the eNodeB has already some knowledge about the kind oftraffic it should allocate some uplink resources for, and can hence takethis into account when issuing the uplink grant; e.g., in case of usingthe D-SR of an SCell, the uplink grant will be larger than when usingthe D-SR of a PCell.

According to another variant of the fourth embodiment, general rules aredefined for the usage of the PUCCH resources (D-SR) for schedulingrequest on PCell and potential PUCCH resources on SCell(s). For exampleUE always starts using PUCCH resources on SCell (if configured) whenrequesting resources for uplink transmissions. Only in case SRtransmission fails on SCell, UE will start using PUCCH resources onPCell. For the case that UE aggregates multiple SCells with configuredPUCCH resources, the UE may select autonomously which of them to use forrequesting uplink (PUSCH) resource, or a prioritization of the SCellPUCCH resources (D-SR) could be applied as outlined in one of thedescribed variations, e.g., according to traffic type, cell type.

Hardware and Software Implementation of the Invention

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. In thisconnection the invention provides a user equipment (mobile terminal) anda eNodeB (base station). The user equipment is adapted to perform themethods described herein. Furthermore, the eNodeB comprises means thatenable the eNodeB to evaluate the IPMI set quality of respective userequipments from the IPMI set quality information received from the userequipments and to consider the IPMI set quality of the different userequipments in the scheduling of the different user equipments by itsscheduler.

It is further recognized that the various embodiments of the inventionmay be implemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

It should be further noted that the individual features of the differentembodiments of the invention may individually or in arbitrarycombination be subject matter to another invention.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A base station comprising: a transmitter totransmit, to a user equipment, configuration information to configure asecond trigger condition for a logical channel of the user equipment,wherein the logical channel is for services that have a tolerance fordelay; and a receiver to receive a scheduling request from the userequipment requesting uplink resources, wherein transmission of thescheduling request from the user equipment to the base station istriggered by the user equipment: determining that a first triggercondition is fulfilled for the logical channel when data becomesavailable in a transmission buffer of the user equipment; starting atimer when the first trigger condition is fulfilled to postponetransmission of the scheduling request; and determining that the secondtrigger condition is fulfilled when the timer expires.
 2. The basestation according to claim 1, wherein the transmission buffer of theuser equipment is used to buffer data to be transmitted in an uplink tothe base station.
 3. The base station according to claim 1, wherein thefirst trigger condition and the second trigger condition are, inoperation, stored in the user equipment.
 4. The station according toclaim 1, wherein the user equipment determining the first triggercondition is fulfilled comprises: determining that new data arrives inthe transmission buffer when the transmission buffer is empty; ordetermining that new data arrives in the transmission buffer with ahigher priority than data already stored in the transmission buffer. 5.A method executed by a base station, comprising: transmitting, to a userequipment, configuration information to configure a second triggercondition for a logical channel of the user equipment, wherein thelogical channel is for services that have a tolerance for delay; andreceiving a scheduling request transmitted from the user equipmentrequesting uplink resources, wherein transmission of the schedulingrequest from the user equipment to the base station is triggered by theuser equipment: determining that a first trigger condition is fulfilledfor the logical channel when data becomes available in a transmissionbuffer of the user equipment; starting a timer when the first triggercondition is fulfilled to postpone transmission of the schedulingrequest; and determining that the second trigger condition is fulfilledfor the logical channel when the timer expires.
 6. The method accordingto claim 5, wherein the transmission buffer of the user equipment isused to buffer data to be transmitted in an uplink to the base station.7. The method according to claim 5, wherein the first trigger conditionand the second trigger condition are stored in the user equipment. 8.The method according to claim 5, wherein the user equipment determiningthe first trigger condition is fulfilled comprises: determining new dataarrives in the transmission buffer when the transmission buffer isempty, or determining that new data arrives in the transmission bufferwith a higher priority than data already stored in the transmissionbuffer.
 9. A method executed by a user equipment, the method comprising:receiving, from a base station, configuration information to configure atrigger condition for a logical channel of the user equipment, whereinthe logical channel is for services that have a tolerance for delay;determining a buffer status report is triggered when data for thelogical channel becomes available in a transmission buffer of the userequipment; starting a timer when the buffer status report is triggeredto postpone transmission of a scheduling request; determining thetrigger condition is fulfilled when the timer expires; and transmittingthe scheduling request based on determining that the trigger conditionis fulfilled.
 10. The method according to claim 9, further comprising:buffering data to be transmitted in an uplink to the base station in thetransmission buffer.
 11. The method according to claim 9, furthercomprising: identifying uplink resources allocated to the user equipmentbased on the scheduling request; and transmitting the buffer statusreport to the base station in the uplink resources.
 12. The methodaccording to claim 9, wherein determining the buffer status report istriggered further comprises: receiving data for the transmission bufferwhen the transmission buffer is empty; and determining the buffer statusreport is triggered based on receiving the data for the transmissionbuffer when the transmission buffer is empty.
 13. The method accordingto claim 9, wherein the data is first data and determining the bufferstatus report is triggered further comprises: receiving the first datafor the transmission buffer; determining the first data has a higherpriority than second data stored in the transmission buffer at a time ofreceiving the first data for the transmission buffer; and determiningthat the buffer status report is triggered based on receiving the firstdata with the higher priority.
 14. A user equipment comprising: atransmission buffer to buffer uplink data to be transmitted to anetwork; processing circuitry coupled with the transmission buffer, theprocessing circuitry to: receive, from the network, configurationinformation to configure a trigger condition for a logical channel ofthe user equipment, wherein the logical channel is for services thathave a tolerance for delay; determining a buffer status report istriggered when data for the logical channel becomes available in thetransmission buffer of the user equipment; starting a timer when thebuffer status report is triggered to postpone transmission of ascheduling request; determining the trigger condition is fulfilled whenthe timer expires; and transmitting the scheduling request based ondetermining that the trigger condition is fulfilled.
 15. The userequipment according to claim 14, further comprising: identifying uplinkresources allocated to the user equipment based on the schedulingrequest; and transmitting the buffer status report to the network in theuplink resources.
 16. The user equipment according to claim 14, whereindetermining the buffer status report is triggered further comprises:receiving data for the transmission buffer when the transmission bufferis empty; and determining the buffer status report is triggered based onreceiving the data for the transmission buffer when the transmissionbuffer is empty.
 17. The user equipment according to claim 14, whereinthe data is first data and determining the buffer status report istriggered further comprises: receiving the first data for thetransmission buffer; determining the first data has a higher prioritythan second data stored in the transmission buffer at a time ofreceiving the first data for the transmission buffer; and determiningthe buffer status report is triggered based on receiving the first datawith the higher priority.
 18. An apparatus comprising: memory to storeconfiguration information; and processing circuitry coupled with thememory, the processing circuitry to: generate a message to betransmitted to a user equipment, the message having the configurationinformation to configure a trigger condition for a logical channel ofthe user equipment, wherein the logical channel is for services thathave a tolerance for delay; and process a scheduling request from theuser equipment, the scheduling request to request uplink resources,wherein transmission of the scheduling request from the user equipmentis triggered by the user equipment: determining a buffer status reportis triggered when data for the logical channel becomes available in atransmission buffer; starting a timer when the buffer status report istriggered to postpone transmission of the scheduling request;determining the trigger condition is fulfilled when the timer expires;and transmitting the scheduling request based on determining that thetrigger condition is fulfilled.
 19. The apparatus according to claim 18,wherein the processing circuitry is further to: allocate uplinkresources based on the scheduling request; and receive the buffer statusreport in the allocated uplink resources.
 20. The apparatus according toclaim 19, wherein the processing circuitry is further to: receive thedata for the logical channel in the allocated uplink resources.